Mortal Once More

July, 1981

Regulus takes a deep breath, trying to ignore the nerves writhing in his stomach. If anyone had told him, a year ago, that he would be willingly coming to Sirius’s apartment, readying himself to go on a mission with his brother to take the Dark Lord down, with an extremely reluctant Kreacher in tow…

He presses a hand to his pocket, feeling the reassuring weight there, steels himself for a moment, and raps sharply on the door. 

He’s already trying to prepare his most disdainful, unaffected expression, readying himself for his brother’s glare - but it’s Fabian who answers the door. 

“Alright there, ‘just Regulus’?” Fabian asks, grinning as he catches sight of his deliberately haughty expression. Regulus feels something deep in his chest stutter, despite himself. “You don’t look all that relaxed, I must say,” the tall redhead continues. “Anyone would think you were about to do something scary - you’re just paying a visit to your brother, aren’t you?” 

Regulus can’t help but notice that Fabian’s teasing grin doesn’t quite reach his eyes. His gaze isn’t bright with mischief today - Regulus can see the anxiety, just barely covered by his smile. Clearly, Fabian thinks it’s his duty to cheer everyone around him up with jokes and teasing banter - even when he’s just as worried himself. 

“I don’t know, I think Sirius can be pretty scary when he wants to be,” Regulus confesses, finding himself grinning back at Fabian. What the hell is wrong with me? “Don’t tell him I said that, though, I’d never hear the end of it.”

Fabian lets out a surprised huff of laughter, his eyes becoming a little brighter, his grin more genuine as he looks at him. Regulus finds himself glad that he’s managed to distract Fabian from his worrying, even if only a little - and he’s surprised to find that he feels a bit less anxious, too, once he meets the other man’s teasing in turn. 

“I’m guessing this is the famous house elf who knows how to get us there?” Fabian asks, looking away and nodding down at Kreacher, who’s skulking behind Regulus’s legs. 

Regulus blinks, feeling a little dazed for a split second, wondering how long he’d just been looking at Fabian’s freckled face. 

“Uh, yeah,” he says, mentally shaking himself, “this is Kreacher.” 

Fabian gives the elf a grin and waves cheerily down at him.

“Hi, Kreacher!” he says. “Fabian Prewett.”

Regulus can’t help but stare at him - he’s never really seen anyone else speak to Kreacher like that, as if they were just introducing themself to another person. Sirius certainly never did. 

Kreacher doesn’t seem to appreciate the friendly gesture, though.

“The Prewetts are blood traitors,” the elf croaks, shrinking back and looking up at Fabian as though he’s a piece of dirt stubbornly clinging to one of the Blacks’ silver goblets. “Kreacher knows this, everyone knows this…oh why, why has Master Regulus brought Kreacher here?”

“Kreacher!” Regulus hisses, heat creeping across his cheeks, mortified as he watches the grin vanish from Fabian’s face. 

“No, that’s alright,” Fabian says coolly. He peers down at Kreacher, eyebrows raised, his expression less friendly than Regulus has ever seen it now. 

“You know what, Kreacher? I am a blood traitor - and proud of it, too. But you can bet that I still treat ‘Master Regulus’ here a damn sight better than your beloved noble family does.” 

Regulus stares at him, feeling even more mortified now as his cheeks burn. He’s never heard anyone else except Sirius proclaim that they’re proud to be a blood traitor. And speaking of Sirius, just what has he been telling Fabian about him?

“Anyway, unless Kreacher here has anything else that he desperately needs to tell me,” Fabian says - Regulus looks down at the carpet, hearing the annoyance in his voice - “I think we’d better go tell the others that you’re here. About time, too - Remus didn’t even notice me stress-eating his precious chocolate, the pair of them have been busy bickering for about half an hour already.” 

Regulus rolls his eyes and sighs at this. But as he follows Fabian into the living room, casting Kreacher a warning glance, he hopes the other man can’t tell that his heart is in his throat, his anxiety choking him. 

How the hell are he and Sirius supposed to just…cooperate? 

“For god’s sake, Sirius, you don’t have to come!” Lupin is sniping exasperatedly, as they walk into the living room. 

Fabian hadn’t been joking, apparently - the two of them are evidently so wrapped up in their argument that they hadn’t even heard the conversation happening out in the hallway. 

“Dumbledore didn’t even invite you, you just barged your way into the discussion -”

“Yeah, I remember that, thanks, Moony,” Sirius snaps back. “I’m fully aware Dumbledore thinks I just cause trouble -”

“Because you’re doing such a good job of disproving that theory right now,” Lupin interjects, rolling his eyes. 

“But like I said, there’s no way I’m leaving you alone with him ,” Sirius continues loudly, as though he hadn’t heard his boyfriend’s sarcastic comment. 

“Sirius, we’ve been through this! I can deal with your little brother, I am every bit as capable as you, and a damn sight less reckless! You need to stop being so bloody overprotective. Or is there something else you’re implying?” 

Lupin narrows his eyes dangerously, and for the first time in his life Regulus sees his brother backtrack, looking slightly sheepish.

“I didn’t…I’m just trying to keep an eye on…”

“Look,” Lupin growls. “I know you can’t stand him, that’s probably why Dumbledore didn’t want you involved in the first place. You’re more than welcome to stay here and let me and Fab handle him, you can swap duties with Fab, if you like, go and help Gid tonight. In fact, I think I’d prefer it that way…”

“No!” Sirius insists, sheepish expression disappearing as he glares at Lupin. “I told you, Moony, I’m coming. You aren’t getting rid of me that easily.” 

“Fine,” Lupin sighs, sounding exhausted now. “But for the love of God, can you stop being such an obnoxious prick ? Just for a few hours?” 

“Ahem,” says Fabian, grinning. Remus and Sirius look round, looking almost comically surprised at the interruption. “Hate to break up the lovers’ spat - but we’ve got a visitor here, boys. Well… two visitors, actually. And correct me if I’m wrong, but I seem to remember we had something pretty important scheduled tonight. Other than a shouting match in the living room, I mean.” 

Remus takes a deep breath, apparently trying to calm himself down - but Sirius’s face darkens further. He doesn’t actually look at Regulus properly, though, his scowl landing instead on Kreacher. 

“Oh, wonderful, ” he says, his tone dripping with sarcasm. “Fab, you didn’t actually have to let that senile, vindictive little git of an elf into our apartment as well, you know. Could have left him outside, he would have been just fine.”

“Shut up, Sirius,” says Regulus loudly before he can stop himself, glaring at his brother. 

Fabian and Lupin stare at him in surprise, and it’s only then that Regulus realises that was the first time he’d spoken directly to Sirius in over two years. Sirius actually looks directly at him - without meaning to, Regulus assumes - his eyes widening slightly. Before he can respond, though, Kreacher pipes up with his bullfrog’s croak. 

“Young Master Sirius can try to insult Kreacher, but it will not work, no, because Kreacher knows that Master Sirius is a spiteful, foolish little blood traitor who broke his mother’s heart by running away from home -”

‘Well, you’re really making me regret that decision now, Kreacher,” Sirius snarks. 

Regulus tries to swallow against the lump in his throat. He already knew, of course, that his brother had absolutely no regrets about leaving him behind in that house - no point getting upset at the reminder. 

“How is dear old Mum, by the way?” Sirius asks loftily, apparently addressing Regulus but fixing his gaze somewhere behind his shoulder. “Still a complete and utter bitch, I presume?” 

“I think we should run over the details for this mission,” says Fabian hastily, as Kreacher swells with fury, letting out a sound remarkably similar to a kettle boiling on a stovetop. “I’m very excited to go on this adventure with you boys, obviously, but first things first, I did have one question to get out of the way - just what exactly is a Horcrux?” 

The others stare at him. 

“What?” Fabian asks, annoyed. “I mean, I’m assuming it must be something pretty dark if You-Know-Who has got one and we’re going to destroy it. Excuse me for not being completely up to scratch with my dark magic. You guys seemed to know what it was, so I didn’t want to slow the meeting down by asking Dumbledore. Plus, he never gives any straightforward answers, anyway.” 

Regulus snorts a little - that’s certainly true. Fabian looks at him, raising an eyebrow indignantly, apparently thinking Regulus is mocking him for his ignorance. Which, to be fair, doesn’t sound completely implausible. 

“Well, go on then, Master of Mystery,” he huffs, putting his hands on his hips dramatically, although his grin rather ruins his attempt to look annoyed. “What, precisely, is a Horcrux? Enlighten me.” 

Regulus opens his mouth, but Sirius gets there first. 

“It’s an object in which a Dark witch or wizard has hidden a fragment of their soul, so they can become immortal. The only way to create one is to split your soul through murder, then use a spell to encase the torn portion inside an object. It’s the darkest kind of magic there is.” 

This time, everyone is staring at Sirius. He squirms a little, looking more uncomfortable than Regulus has seen him in a long time. 

“Our parents had some really messed up books in the family library,” he mutters, with a shrug. “I used to get bored when I came home from school sometimes. And I’ve got a good memory.” 

“He murders…to split his soul?” 

“Amongst other reasons, I assume,” Lupin says wryly. “Given that there’s only one Horcrux that we know of, and he’s murdered quite a lot of people.”

“And he’s made himself immortal?” Fabian asks, looking thunderstruck.

“Sounds like it,” Sirius replies, his face grim. “That is, assuming my brother’s information can actually be trusted.” Regulus shoots a glare at him.

“Well…shit,” says Fabian. Regulus lets out a humourless laugh.

“Quite.” 

“The locket that the Dark Lord placed in the basin?” Kreacher croaks suddenly, looking horrified. “It’s a - ” 

“Kreacher,” says Regulus quietly, flashing him a warning glance. “Remember what I said, please. Not one word about this to anyone outside of this room - and especially not to my mother, you understand?”

The elf nods reluctantly. 

“Okay, so, the plan is to steal a piece of You-Know-Who’s soul ,” says Fabian, clearly still trying to wrap his head around this revelation, “which is hidden inside a bloody locket , of all things?”

“Yes,” Regulus replies bluntly. “Salazar Slytherin’s locket, to be precise.” 

“....Alright,” says Fabian. Regulus can see he’s trying to choose from around a thousand questions he wants to ask. “I assume the plan is to destroy it, once we’ve stolen it?”

“Well…” says Regulus, feeling more than a little uneasy, wishing Fabian would stop looking at him like he was the fount of all knowledge, “...yes, of course that will be the next plan.” 

“So? How do you destroy a Horcrux, then?” 

“Well…” says Regulus slowly, looking away from those bright blue eyes, finding that curious gaze a bit overwhelming at the moment, “ Secrets of the Darkest Art was sort of focused more on the creation of Horcruxes, rather than the destruction….I suppose because Dark wizards wouldn’t tend to be looking for instructions on how to destroy their own soul receptacles…”

“What?” Fabian exclaims. “Are you telling me we’re about to walk into a death trap to nick a piece of You-Know-Who’s soul, and you don’t actually have any idea how to destroy the damn thing?” 

“I have some idea,” Regulus replies, defensive now. “The book warned about Basilisk venom, apparently it’s an incredibly destructive substance for Horcruxes…”

“Oh well, thank God for that then,” Lupin quips. “I was wondering what to do with my endless jars of Basilisk venom, they’re taking up too much valuable space on my bookshelves.” 

Regulus glares at the scarred man, even as Sirius bites back a grin, sneaking an adoring sideways look at him. 

“Look,” he huffs, “we will figure out how to destroy it. There are ways, and I will do more research. But right now, it seems to me that we have to first get at the thing, before we can destroy it.” 

Silence for a moment.

“Seems logical to me,” says Fabian, with a small grin.

“Yes, I thought so,” Regulus replies, deadpan, trying to resist the stupid impulse to grin back at him. 

“Not to be a killjoy,” Sirius pipes up loftily, “but there seems to be one tiny flaw in your plan.” It’s impressive, really, Regulus thinks, with another sharp twinge of hurt, how Sirius still manages not to actually meet his eyes, even when he’s speaking directly to him. “If we nick this Horcrux, don’t you think Voldemort is going to notice that the basin he left it in is strangely empty?”

“Well, you’re assuming that he’ll go back and check it at any time soon. At the moment, he’s convinced that it’s safe, and there’s nobody alive who even knows of its existence. You’re forgetting how arrogant he is. And anyway,” Regulus continues smugly, “even if he does decide to go back and check, I’ve already got that covered.” 

Smoothly, he reaches down and pulls a large golden locket out of his pocket, holding it by the chain and dangling it in front of the others so they can see it clearly. Kreacher lets out a squawk of horror, as Regulus had known he would. 

“Is that a Black heirloom?” Sirius asks, sounding astonished. “Did you actually…take that from the house behind Mother’s back?” 

“Yes, and yes,” Regulus replies, with another smug grin. 

Sirius raises an eyebrow, and Regulus can tell he’s trying not to look impressed. 

“Well,” he says. “Looks like the mummy’s boy might finally be trying to grow a spine.” 

Regulus chooses to ignore that.

“And if the Dark Lord ever does go back to check his ‘Horcrux’, he continues, “he’ll find that it suddenly contains a note inside.” 

He clicks the locket open, taking said note out and holding it up to show the others. 

Fabian reaches out to take the note from him, unfolding it. 

“ To the Dark Lord ,” he reads aloud. “I want you to know that it was I who discovered your secret. I have stolen the real Horcrux and intend to destroy it as soon as I can, in the hope that, when you meet your match, you will be mortal once more.

R.A.B.”

“What’s the ‘A’ stand for?” Fabian asks curiously. 

“Arcturus,” Regulus mumbles, and he and Lupin both snort.

“ God, you Blacks are poncey,” Lupin mutters. 

“But…I don’t really get it, Regulus,” Fabian confesses, a faint frown line appearing between his eyebrows. For one mad moment, Regulus has a strange urge to smooth the crease away with his thumb. “Why write this note? You-Know-Who isn’t actually going to read it, is he?”

“Well, I haven’t actually signed my name ,” Regulus points out stubbornly, “just my initials. And he’ll probably see that note one day - hopefully after we’ve already destroyed the Horcrux. Assuming he actually realises who ‘R.A.B’ is” - he had written his initials, not just for the sake of anonymity, but as a kind of test for the Dark Lord, to see if he could look past his own arrogance long enough to connect the dots - “then that’s just fine with me. I want him to know, in the depths of his panic, that it was me who discovered his secret. Me that set out to bring him down.” 

The others stare at him for a moment, in shocked silence. Then, to his surprise, Lupin bursts out laughing, throwing his head back. 

“God, Dumbledore is right, you know,” he says, shoulders still shaking with laughter as he looks back and forth between Regulus and Sirius. “You two really do sound just like each other, sometimes.” 

The two brothers both glare at him, but that doesn’t stop him; in fact, Fabian starts laughing, too. Regulus notices, though, that there’s a nervous, hysterical edge to their laughter - they really are going to do this. 

“Yes, well, if you two are done acting like children,” he says haughtily, “I think we really ought to go. Don’t you?” 

Fabian and Lupin stop laughing abruptly at that. Everyone glances at Regulus uneasily in the sudden silence; there’s nothing to mask the tension now. Fabian takes a deep breath and nods. 

“You’re right, Regulus,” he says. “No time like the present, after all. I’ve probably kept us waiting long enough as it is, making you lads give me a crash course in Horcruxes.” 

It’s very characteristic of him, Regulus muses, to take the blame for delaying them, when if anything it was Sirius acting like a dick that caused the hold up, as per usual. 

“Alright, I think Kreacher should probably take us there in pairs,” he says briskly, trying to sound businesslike and hoping the others can’t tell that his heart has lodged itself somewhere in his throat. “You two go ahead of us,” he says, nodding at Sirius and Lupin, though carefully not looking directly at his brother. “Just wait on the spot where Kreacher leaves you, we’ll be right there.”

Neither Sirius nor the elf moves; they’re both just standing there, glaring at each other with the utmost loathing. 

“Oh, for god’s sake,” Lupin mutters, rolling his eyes. Irritably, he moves forward, seizing Sirius with one hand, and holding his other hand out to Kreacher. “We’re ready when you are, Kreacher,” he says firmly, and Regulus feels a twinge of gratitude towards him. 

Kreacher doesn’t look much happier with this; but when he glances over at Regulus, who nods, the elf scowls and reaches out to grasp Lupin’s spare hand. A moment later, all three of them vanish with a loud crack . 

It feels stranger than Regulus had expected, being suddenly entirely alone with Fabian. The living room suddenly feels much smaller; he steps a little further away, and the tall man gives him a slightly bemused smile. 

“Well, this should be painless, eh?” Fabian quips, raising an eyebrow at him. 

Regulus barely has time to wonder if he means the mission, or spending time with him , before Kreacher appears again with another crack , already trembling from having been in the vicinity of the cave for just a few moments. 

“Hey…it’s alright, Kreacher, you’re safe,” Regulus murmurs, kneeling down so they’re at the same level. The elf looks at him and gives a shaky nod. Regulus smiles at him reassuringly and stands up again, heart lodged in his throat again as he looks over at Fabian. 

“Ready?” he asks. The redheaded man takes a deep breath.

“Ready as I’ll ever be,” he declares. 

Before Regulus knows it, Fabian has reached out, taking his hand gently in his own. He jumps slightly as Fabian’s calloused palm presses against his own - the other man’s skin is warm. 

Regulus takes a slow, shaky breath, holding his other hand out to Kreacher. 

The elf turns on the spot, and Regulus feels the familiar sensation of being squeezed through a thick rubber tube. A moment later, the invisible bands pressing his chest seem to burst open, and the three of them are standing in cool darkness next to Sirius and Remus, breathing in lungfuls of fresh, salty air. 

Still trying to orient himself, Regulus glances around to see that the five of them are standing on an outcrop of dark rock, water foaming and churning all around them. A towering cliff stands across from them, and the view out across the sea is bleak and unforgiving, grey waves crashing relentlessly against the foot of the cliff. 

“Bloody hell,” Fabian comments in awe, over the roaring sound of the waves. “You-Know-Who has quite the sense of drama, doesn’t he?” 

Regulus can’t help but shiver slightly.

“Hey - you alright?” Fabian asks, his voice full of gentle concern, much more quiet this time, so that only Regulus can hear him.

“Fine,” he mutters without meeting his eyes, mortified that the redhead had noticed his unease. 

Turning to Kreacher, who still hasn’t dropped his hand, Regulus sees immediately that his nerves are as nothing compared to the elf’s; he’s trembling all over, eyes wide and terrified as he stares across at a narrow fissure in the cliff, where dark water is rapidly swirling. 

“Lumos,” he mutters, holding his wand up so that the golden light illuminates the gap in the rock. 

“Is that where we have to go, Kreacher?” he murmurs. 

He and Lupin shouldn’t have too much of an issue, he thinks, but that gap scarcely looks wide enough to accommodate Fabian and Sirius, who both have much broader shoulders. 

Kreacher nods jerkily. 

“Master will have to…to get in the water,” the elf croaks, trembling at the memory.

“And then we’ll be in the cave?” he asks. 

This time Kreacher shakes his head. 

“There is an antechamber of rock,” he explains. “Payment is required to pass through.” 

“ Payment?” Lupin echoes, sounding bemused. 

“Payment in blood,” the elf clarifies, his voice shaking. “The Dark Lord requires others to weaken themselves before passing through. The Dark Lord made Kreacher cut himself.” He squeezes his eyes shut, as though willing himself to be anywhere else. 

Regulus feels a dark surge of rage at this, mingled sickeningly with guilt. He thinks back to the night he’d called Kreacher home, trying to remember every detail. Had he even noticed, in his panic, that the elf was bleeding? 

He crouches down so he’s at eye level with Kreacher again, reaching out to grasp his bony little shoulder gently. He sees Sirius’s expression of mingled disgust and bewilderment out of the corner of his eye, but at the moment he couldn’t care less. 

“Thank you for bringing us here, Kreacher. I know how hard it is for you to be back here, and I’m so grateful. But we can take it from here,” he continues, gesturing at the others. “I’m not going to put you in any more danger.”

“But…” says Kreacher, staring at him with wide, terrified eyes. “It is so dangerous , Master Regulus…”

“I’ll manage,” he says grimly, trying to ignore the cold prickle of fear crawling down his spine. “But I need you to go home now - and that’s an order, Kreacher. And you’re not to breathe a word about this to anyone , remember?” he adds sternly.

“But what if Master Regulus does not come back home?” Kreacher whispers, his lower lip trembling.

The fear is inescapable now, like a living thing, clinging to him stubbornly with cold, sharp teeth. Out of the corner of his eye, he sees Sirius make a small, strange, twitching movement. He ignores him, focusing on Kreacher. 

“Hey,” he whispers to the elf. “I’ll see you soon, Kreacher. I promise.” 

He feels another twist of guilt, knowing full well that he can’t promise any such thing. He’s sure Kreacher knows it, too, as he stares at Regulus with his eyes full of tears. The two of them just look at each other for a moment - then, the elf nods, bows, and turns on the spot, vanishing into thin air. 

Regulus takes a deep, shaky breath, standing slowly upright again. 

“Someone’s going to have to cut themself to get in?” Fabian whispers, looking revolted.

“Sounds like it,” Regulus replies coolly, hoping he sounds a lot calmer than he feels. He doesn’t miss the uneasy expressions on the others’ faces. “Look, nobody’s forcing any of you to do this,” he says impatiently. “If it’s too much for you, you can go home, too, and I’ll just…go in there on my own…”

“Not bloody likely,” says Fabian, suddenly fierce. “Three Gryffindors, running away with their tails between their legs and letting a Slytherin play the hero instead? I don’t think any of us would ever be able to look anyone in the face again.” 

Lupin smiles bitterly at that. Sirius, uncharacteristically, says nothing, but Regulus sees his jaw tighten - a sure sign that he’s more likely to sprout wings than back down. 

For his part, Regulus fights to keep his expression neutral, feeling an almost overwhelming surge of relief and gratitude that almost drowns out the fear for a dizzying moment - now he’s here, he honestly doesn’t have a clue if he’d be strong enough to go ahead alone. 

“Alright then,” he says stiffly. “Well…let’s get going then.” 

As it turns out, Sirius and Fabian do fit through the dark slit in the rock face, just about, although it looks like it’s a tight squeeze. The icy water is a shock to the system; Regulus gasps as it hits him, spluttering slightly around the lit wand held between his teeth. 

He’d expected his brother to complain more - but now that they’re here on this mission, Sirius seems completely determined, he and Fabian both swimming ahead with a strong breaststroke. Regulus - like Lupin, it seems - is doing his best to keep up, still gasping with the cold, his waterlogged clothes billowing behind him. Determined not to slow down, he pushes himself harder, following the shimmering light of the others’ wands, moving deeper into the cliff. As they swim, their wands illuminate a dark tunnel opening up ahead of them, the walls barely three feet apart, glimmering like wet tar in the passing light. 

Ahead, Regulus sees Fabian and Sirius rising out of the water, their clothes gleaming. When he and Lupin reach the spot, both of them kicking hard to try and speed up, Regulus notices that there are steps leading up towards a small cave. 

Together, they clamber up them, teeth chattering uncontrollably as water streams from their soaking clothes, emerging into the cold air. Sirius hurries over, reaching his hand out to help Lupin, pointedly ignoring Regulus - but Fabian immediately follows, stretching his own hand out with an encouraging smile. Regulus gives Fabian an awkward nod to signal that he’s fine, resisting the strong temptation to take the hand he’s offering; Fabian almost looks a little disappointed. 

Noticing that both Sirius and Fabian are already dry, he and Lupin immediately follow suit, silently casting drying spells on themselves. Regulus feels a wonderful sense of relief for a moment, his clothes suddenly as warm and dry as if they’d been hanging in front of a blazing fire. 

Slowly, the four of them step forwards, examining the small cave they’re in. Regulus clearly remembers Kreacher describing an eerie greenish glow, shimmering off the surface of the water - but all he can see is the wall of the cave in front of them, a smooth expanse of blank rock. 

“Bit of an anti-climax,” Lupin comments wryly, still sounding somewhat breathless.

Regulus shakes his head.

“Kreacher said there was an antechamber, remember?” he reminds them. “This must be where we have to ‘pay’ to pass through. Look… Revelio. ”

Immediately, an arched outline appears on the rock, blazing bright white, as though there’s a powerful light coming from the other side. A moment later, the outline disappears, the light fading, leaving the rock as bare and solid as before.

“Payment in blood?” Fabian asks uneasily.

“Payment in blood,” Regulus confirms with a sigh, hoping he doesn’t sound as anxious as he feels. 

He lifts his wand, pointing it at his own arm; simultaneously, Lupin does the same. 

“Like hell,” Sirius growls suddenly, making Regulus jump. 

He wonders for a moment if he’s just snarling at his boyfriend; but when he looks up, he sees to his surprise that his brother is glaring fiercely at both of them. 

“Accio,” Sirius mutters, pointing his wand at a particularly jagged-looking rock in the corner, which promptly flies towards him. He catches it deftly, and Regulus watches with his heart in his throat as his brother draws the sharp point of the rock across his arm, without hesitation. Shockingly bright blood bubbles to the surface, like a scarlet blossom against his alabaster skin. 

It’s certainly not the first time he’s seen Sirius bleed, Regulus thinks shakily. He knows that, if he asked, Sirius would say scornfully that he’d done it for Moony , not for him . But still, he can’t help but be reminded of all the times when they were children in a dark house, with nobody in the world but each other, and Sirius had constantly and deliberately infuriated their parents to ensure that he was always the one bearing the burden of their punishments, rather than Regulus. 

“You’re an idiot ,” he hears Lupin saying shakily . “You didn’t need to do that, Sirius, and you know it.” 

“Rather me than you, Moony,” he responds, looking at his boyfriend with a much softer expression than Regulus has seen between them of late. For a moment, he almost feels like he’s intruding. But then Sirius turns back to the blank rock in front of them, seeming to shake himself a little. “Anyway, let’s see if it worked, eh?” 

He presses his arm against the rock face, and the blazing silver outline of an arch appears again. This time, though, it doesn’t fade away; the blood-spattered rock within simply vanishes, leaving a wide opening. Regulus knows immediately that this must be the place; he can see already that the light coming from the other side is distinctly green. His heart seems to have lodged itself in his throat again; and as he exchanges a look with the other three, he can see from their uneasy expressions that they’re feeling much the same way.

“Well,” says Fabian, his voice sounding much louder than usual in the eerie, almost complete silence. “In we go, I guess.” 

He and Sirius lead the way through the archway, and Regulus isn’t surprised when it vanishes again as soon as he and Remus walk through behind them, so that there’s nothing but a wall of solid rock. He supposes the question of how they’re going to get back out is a problem for later. 

The four of them stand in tense silence for a moment, staring at their surroundings. 

They’re standing on the edge of a great black lake, so vast that Regulus can’t make out the distant bank, in a cavern so high that the ceiling, too, is out of sight. The misty greenish light permeating the entire place seems to be shining far away, from what looks like the middle of the lake, reflected in the completely still water below. The green glow and the light from their wands are the only things breaking the velvety blackness, though their wand light doesn’t penetrate as far as Regulus would have expected. The darkness is somehow denser, more ominous than usual darkness. The cave is completely silent in an oppressive, unnerving way. 

“Lovely spot,” says Fabian dryly. His voice isn’t quite as casual as Regulus assumes he’d hoped; but still, it’s a relief to hear someone break the silence. 

“So where might this supposed Horcrux be, then?” Sirius asks, staring around.

“Kreacher said the Dark Lord put it in a basin in the middle of the lake, after making him drink the potion from it,” Regulus murmurs in response, feeling another surge of rage at the memory of the elf’s tale. “I assume it’s somewhere over there,” he adds, pointing to what appears to be the source of the eerie green light. 

“Brilliant,” says Sirius sarcastically. “And just how do you propose we get there? I certainly don’t fancy having a swim in this creepy lake, and I’m a much better swimmer than you .” 

Regulus huffs; apparently Sirius has already exhausted his inclination to be helpful. 

“Kreacher said something about a boat.” 

“A boat? ” Lupin echoes, casting his wand light around the huge expanse of darkness. “Shame he forgot to mention that this boat is invisible.” 

“It’s not invisible,” Regulus scoffs, though he can already feel his heart sinking. Had he somehow misunderstood what Kreacher had said? Perhaps it had been foolish to send him back home so soon? “It’s got to be around here somewhere…”

He casts his wand around, growing more frantic as he sees nothing but black rock, or the reflection of the light on the smooth lake - but then, finally, the wand light catches on something glinting. Something metallic. 

“Look! There!” he says excitedly, and the others cast the light of their wands in the same direction, so that the glinting thing shines in a four-way spotlight. A coppery green chain…

Regulus hurries over, the others in his wake. On closer inspection, he sees that the gleaming coppery chain is hooked into a rock on the ground, anchoring it to the bank on which they’re standing. Acting on instinct, Regulus kneels to clench the chain in his hand - an unpleasant icy sensation that sends shivers down his spine - and taps it gently with his wand tip. He feels another jolt of excitement as it immediately begins to slide through his fist like a snake, coiling itself on the ground with a clinking sound that echoes noisily off the rocky walls, pulling something from the depths of the black water.

Regulus hears the others gasp behind him as the ghostly prow of a small boat breaks the surface of the lake, glowing as coppery green as the chain, and floats with barely a ripple towards the place where they’re staring at it from the bank. He feels relief sweep through him for a moment, releasing a breath he hadn’t even realised he’d been holding. 

“Told you,” he says, turning to the other three with a small, smug grin.

“Bloody hell,” Fabian breathes, staring down at the little boat. “It was just sitting under the lake?”

“Looks like it,” says Regulus, moving tentatively closer to inspect it.

“Uh…Regulus?” says Lupin, moving closer too. “It’s not that big…are you sure it will be sturdy enough to hold more than one of us? I don’t much fancy capsizing here.” 

“It’s nothing to do with weight , it’s to do with…oh, shit,” he curses, his stomach sinking again as he remembers the other thing Kreacher had told him. 

“What?” Lupin asks sharply. 

“I’m an idiot,” Regulus groans. Nobody contradicts him; Lupin just raises an eyebrow, waiting for him to explain himself. “I’ve just remembered…Kreacher said there’s an enchantment on the boat to ensure it can only carry one wizard or witch across the lake at a time. I suppose the Dark Lord wanted to limit the amount of magical power crossing…come to think of it, that’s probably why he needed an elf to test the defences in the first place.” 

“You’re joking,” Fabian says flatly. “After all that, only one of us can actually get to the damn Horcrux thing?” 

Regulus nods, grimacing, wondering why Fabian’s frustration, his disappointment in him, feels so much worse than the others glaring. 

“I’m sorry,” he says helplessly, “I miscalculated. Look, you three wait here on the bank, keep an eye out, and I’ll just go across by myself and take my chances…”

“ ‘Take your chances?’ ” Fabian echoes incredulously. “Like hell! You can’t go across by yourself , Regulus, it’s not bloody safe!” 

“Well, doesn’t really look like we’ve got another option, does it?” Regulus shoots back, glaring at him. Fabian looks so uncharacteristically worried, though, that he finds himself softening. “Look,” he says, more quietly now, “we need to get that Horcrux, Fabian.” 

“Alright, but…” he sounds almost desperate now. “What if we just, I don’t know, Reg, regroup a bit, or…”

“Wait a sec,” Sirius pipes up suddenly, and Regulus realises he’s been uncharacteristically silent during this argument. “Will it help if I do this?” 

Regulus turns around impatiently - just in time to see his older brother transform, with no warning whatsoever, into a huge black dog.

Before he can stop himself, Regulus cries out loudly in shock; Fabian shouts at exactly the same time. The noise echoes loudly, reverberating off the walls of the cave; then, with a sound like a sudden explosion, something very large and pale erupts out of the dark water about twenty feet away. Before Regulus can get a  clear look at it, though, it vanishes again, as abruptly as it had appeared, with a crashing splash that makes deep ripples on the surface of the lake. All four of them leap backwards in shock, hitting the cold wall behind them.

“What the fuck? ” Fabian exclaims, in a sort of whisper-yell - apparently he’s learnt his lesson about making unexpected loud noises in here. 

“Inferi,” Regulus gasps, massaging his chest, his heart thundering so fast that it’s painful. “Kreacher said the lake is full of them, another layer of protection around the Horcrux. They nearly killed him when the Dark Lord left him here.” 

“ Brilliant,” Fabian mutters. “You know, sometimes I think I should give it a rest with trying to help people. Tell Dumbledore I just want to drink tea and play Quidditch for a bit. And since when can he do that ?” he asks, frowning at Lupin as he points at the large black dog which had a moment ago been Regulus’s infuriating brother. 

“I was going to ask the same question there, Lupin,” Regulus adds, staring at the dog, which is panting excitedly as it looks up at them, and behaving much better than Sirius ever does. 

“Oh…yeah, he’s an Animagus,” Lupin replies, unhelpfully.

“I think we got that part, thanks,” Regulus deadpans. 

“He’s been one since he was fifteen,” Lupin elaborates. “That’s why we call him Padfoot. James and Pete are Animagi, too - James is Prongs because he turns into a stag, Pete’s Wormtail because he turns into a rat. None of them are strictly registered or legal , obviously, so maybe don’t rush to mention it to Dumbledore - or McGonagall,” he adds, with a sheepish grin. 

“Bloody hell,” Fabian mutters again. “Y’know, when I said we weren’t going to run away with our tails between our legs, nobody mentioned that that was literal for some of us.”

“They did it to help me,” Lupin explains. 

“Help you…?” Regulus echoes, frowning in confusion.

Lupin’s eyes widen suddenly, as though realising he’s put his foot in his mouth. Dog-Sirius looks sideways at him, his ears drooping.

“I…don’t worry about it,” he mutters, looking away. “Not important.” 

Regulus frowns, staring at him. 

Sirius and the others always call him ‘Moony’...He thinks about the way Lupin almost always looks pale and fragile and a little ill, how scarred he is. Remembers how Sirius had always seemed so protective of him. Remembers Snape’s dark mutterings and insinuations, which at the time even most of the other Slytherins had ignored, given his weird obsession with getting Potter and his gang into trouble. He remembers the map of Britain he’d seen on Lupin’s desk, with the scattered red pins, which Lupin had hastily rolled up when he’d caught him looking. Remembers how Dumbledore had suggested he might want to join Regulus so he could have a break from his ‘monthly missions’...

Oh. 

He’s distracted from this latest revelation when the black dog - his brother, Regulus reminds himself bemusedly - nudges his fallen wand towards Lupin with his nose, before quietly padding over to the little boat. He looks back at the other three, his ears perking up again as he places one huge paw on the prow of the boat. 

“I think Padfoot is wondering whether he’s found a loophole in Voldemort’s enchantment,” Lupin murmurs, staring at Sirius, hazel eyes wide in his pale, scarred face. He bends to pick up the wand Sirius had nudged towards him. “I should probably go across with him, make sure he’s -”

“No, I already told you, I’m going,” Regulus growls. “ I’m the one with the replacement locket. I’m the one who wrote the letter.” 

Lupin glares back at him, clearly on the brink of arguing; Regulus can see how scared he is at the thought of letting Sirius cross the lake without him. But Regulus folds his arms, raising one haughty eyebrow and jutting his chin out defiantly, and Lupin sighs, closing his mouth and nodding reluctantly. Perhaps he’s simply had enough experience with Sirius to recognise when arguing is futile. 

“Fine,” he mutters, holding Sirius’s wand out to him. “But you better bloody keep him safe .” 

“I’ll do my best,” Regulus replies, cold dread swirling in his stomach as he tucks his brother’s wand in his belt, next to his own. He checks for the weight of the locket again, to reassure himself.

The black dog, already sitting in the little boat, huffs loudly. Typical Sirius - he might have an abundance of words usually, but it turns out he doesn’t need any of them to communicate his disdain. 

“What should Remus and I do, then?” Fabian asks quietly. 

“Just…stay here and keep your wands ready,” Regulus murmurs. “We could get into trouble at a moment’s notice, but you two should still be able to help us from here. Inferi are terrified of light and warmth.” 

“Fire,” Lupin murmurs. He nods. 

“Regulus…” Fabian starts. He turns to look at him. “Be careful,” he says, looking more anxious than Regulus has ever seen him. He seems to hesitate for a moment - then he reaches out and squeezes his shoulder gently. Regulus feels his stomach do another backflip, fear and anxiety and adrenaline mingling with…something else. “I mean it,” Fabian adds, expression completely earnest as bright blue eyes meet cool grey. 

“Yeah,” Regulus answers shakily. “We’ll do our best.” 

“What, you and Sirius?” Lupin asks, cynical. “Careful? Somehow I doubt that.” 

Regulus lets out a shaky chuckle, as his brother’s boyfriend looks over at the black dog sitting in the boat, his hazel eyes shining with fear and love. He turns back to Regulus.

“ Please will you two try not to kill each other before Voldemort gets a chance to?” Lupin begs. 

Despite the fear creeping down his spine, Regulus can’t help but grin a little at that.

“Well, I can’t speak for him,” he responds, jabbing a thumb in the direction of the large dog. “But I’ll try not to. No promises, though.” 

Regulus steps awkwardly into the little boat, unhooking the coppery green chain from the rock. His heart pounds wildly for a moment, terrifying images flashing through his mind. What if Sirius transforming hasn’t made any difference to the boat’s enchantment? What if they capsize into the icy lake, as soon as the bank is out of sight? 

But to his immense relief, the loophole that his brother had found seems to work; the little green boat glides smoothly across the lake, as though an invisible rope is pulling it towards the green light in the centre. 

He darts a sideways glance at the huge black dog, which has pointedly turned its back on him, staring out towards the green light. It occurs to Regulus that this is the first time in over five years that he’s actually been alone with his brother; he can hardly think of stranger circumstances. He thinks of all the times over the years that he’d longed for the chance to speak with Sirius, alone, away from their parents, away from his brother’s friends or his own - but now, he’s surprised to find he’s relieved that Sirius is currently a dog and unable to converse at all, for a few moments at least. Regulus doesn’t think he’d know where to begin, anyway. 

As they cross the lake, there’s no sound at all other than the beating of his own heart, and the silken rustle of the boat’s prow cleaving the water. Regulus looks down and sees the reflected gold of his wand light, sparkling and glittering on the dark water as they pass, the boat carving deep ripples on the glassy surface…

And then the light from his wand illuminates a fresh patch of water and shows him, without warning, a dead man lying face up inches below the surface; marble-white, his open eyes misted as though with cobwebs, his hair and robes swirling around him like smoke. 

Regulus gasps loudly before he can stop himself, his heart lodged in his throat again. The black dog looks over at him, ears twitching nervously, and somehow Regulus can recognise his brother’s anxiety even through the canine features. For the first time in a very long while, he feels as though a tiny moment of understanding passes between them, however brief. He swallows, looking determinedly away from the water, raising his wand so it illuminates the path ahead. He feels stupid for being so shocked, it wasn’t as if he hadn’t already known about the Inferi… Why am I doing this again? 

He focuses on the eerie green light ahead of them, willing himself to calm down. He notices suddenly that they’re very close to it now, the light seeming to grow much larger; within minutes, the little boat comes to a halt, bumping gently into something solid. Raising his illuminated wand, Regulus sees that they’ve reached a small island of smooth rock in the centre of the lake. 

The black dog jumps out immediately, apparently with no hesitation at all - typical , Regulus muses. He climbs out behind him, grateful to be on solid land again, and turns to hook the coppery chain to the rock, his hands trembling a little. By the time he turns around, Sirius is standing in the place where the black dog had been, staring down at the source of the strange green light, his expression thoughtful and concerned. Without looking up, he holds his hand out, silent and expectant; Regulus takes his brother’s wand out of his belt and gives it to him. 

The light seems much brighter, close up; Regulus sees that it’s coming from a stone basin, almost like a Pensieve, set atop a pedestal. He and Sirius look down at it together; the basin is full of an emerald liquid, emitting a phosphorescent glow. Just as Kreacher had described. 

“So…not a health drink, I’m assuming?” Sirius breaks the silence, without looking up at him.

“Most assuredly not, according to Kreacher,” Regulus answers. 

“And you think the Horcrux is at the bottom?” 

Regulus shakes his head. 

“I don’t think it is, I know it is. Kreacher saw the Dark Lord put it there.” 

“I see,” Sirius replies, still frowning down at the basin. “Well, I hope this isn’t just one of those stupid ideas you tend to get into your head.” 

“ You can talk about stupid ideas,” Regulus mutters. 

Sirius actually looks up at that, a surprised grin on his face despite himself.

“Can’t we just…lift the basin up and pour all this crap into the lake, and get at the Horcrux that way?” he suggests.

Regulus shakes his head again. 

“Kreacher said the Dark Lord has enchanted it so you can’t Vanish it, or Transfigure it, or pour it away, or anything like that. The only way to get rid of it is to drink it.” 

“Right,” Sirius sighs. “Of course. Bloody typical.” 

“And…” Regulus hesitates for a moment, but figures that his brother needs to know. “Kreacher told me that drinking this potion was agony. Well, he said it wasn’t exactly physically painful, but…apparently it made him remember all of the worst things that had ever happened to him, all at once. Sort of like Dementors, you know?” 

Sirius stares at him for a long moment, the colour draining from his face. 

“So…” says Regulus slowly, cold dread coiling in the pit of his stomach at the task ahead of him, “if I start crying, or yelling, or -”

“Wait a second,” Sirius interrupts him sharply. “What do you mean, if you start crying? You’re not going to be drinking this thing, Regulus. I am.”

Regulus stares at him stupidly; his brain seems to be taking a long time to process his brother’s words. 

“Wait…what?” he whispers, ice seeming to creep across his chest. “No…you can’t… I was going to drink it, Sirius!” 

“Well, tough shit, little brother,” he responds. “You’re not now. You can supervise me - you’ve got a lot of experience in that area, don’t you?” 

He ignores that jab.

“Sirius, I wasn’t going to ask you to -” 

“You didn’t have to ask me, because I’m telling you,” Sirius shoots back. “I’m drinking it, you’re not. Simple.” 

Regulus wants to yell at him, to scream - nobody has ever been able to infuriate him as much as his brother. But Sirius has an all-too-familiar expression of fierce determination on his face, and he knows that his mind is made up. The two of them stand there for a moment, glaring at each other. 

“I was always tougher than you, anyway,” Sirius mutters, and Regulus lets out a reluctant laugh. 

Obviously another jibe, another barbed implication that he’s weak for going along with their parents’ wishes for so long. And yet, at the same time, Sirius’s stubborn insistence that he has to be the one to drink this hellish potion, to suffer this pain, reminds Regulus so strongly of all the times his brother had tried to protect him from their parents when they were children that he feels almost dizzy with nostalgia, overcome with emotion that he has to fight to hide. 

He will never understand Sirius. 

Sirius, oblivious as always to his turmoil, twirls his wand, conjuring a goblet from midair. Regulus’s throat goes dry at the sight of it, his heart pounding with terror again. 

“You’d better make sure I keep drinking this crap,” Sirius says. Regulus can see the fear in his grey eyes, though he’s trying hard to hide it, to sound casual. “If I start kicking up a fuss, just…ignore me. You know I can be a bit of a drama queen.”

“Sirius…”

“ Promise me , Reg.” 

He looks at his brother’s fierce face, the stormy eyes, the chin defiantly jutted out, feeling for a moment like he’s looking into a mirror. 

Regulus bites his tongue, and nods reluctantly. 

At that, Sirius sinks the goblet into the green potion, so abruptly that Regulus can tell he wants to get on with it before he can betray any fear. When it’s full to the brim, Sirius raises it to Regulus, in a sarcastic toast, and drains the whole goblet in one go. 

Regulus watches in terror, gripping the side of the basin so hard that he can’t feel his fingertips. 

“Sirius?” he asks anxiously. “How do you feel?”

Sirius just shakes his head, his expression completely blank. Regulus feels an icy chill creep down his spine - his brother has always been awful at hiding his emotions. He’s never seen him with no expression on his face at all; it’s unnatural. Eerie. 

“Sirius?” he asks again, wondering whether he’s in pain. 

But Sirius doesn’t even seem to hear him; blindly, he plunges the goblet into the potion again, as though following some instruction that Regulus can’t hear, refills it to the brim, and drains it for a second time. Regulus watches, heart pounding in terror, as he does the same with a third goblet, still completely silent, face still unnaturally blank. God, how much potion is there in this basin? he wonders, glancing down - Sirius barely even seems to have made a dent yet. 

Then, halfway through the fourth goblet, he suddenly staggers, falling forwards against the basin. 

“Sirius?” 

Regulus stares at his brother; his eyes are closed now, his breathing shallow, his face twitching violently as though he’s asleep but having a terrible nightmare. Sirius’s grip on the goblet slackens, the potion almost spilling from it; Regulus hastily reaches forwards to steady it. He has a horrible feeling that if any of it spills on the ground, the basin will immediately refill. 

“Sirius? Can you hear me?” 

His voice sounds so embarrassingly small and pleading that at any other time he’d have been mortified; but right now, waiting for Sirius to respond, hoping desperately that he’ll open his eyes, roll them at him and mock him as usual, Regulus couldn’t care less. 

Instead, Sirius pants and speaks without opening his eyes, speaks in a voice that terrifies Regulus more than anything else has tonight, because his cocky, sarcastic older brother sounds suddenly like a small and frightened child. 

“No…no…I don’t want…don’t make me…”

Regulus stares into his brother’s face, the face he knows almost as well as his own, and has no idea how to help him.

“ Please …I don’t like it…make it stop…”

“You…you can’t stop, Sirius,” Regulus says desperately. “You told me to make sure you keep drinking, remember?” 

Hating himself, repulsed by what he’s doing, he forces the goblet back towards Sirius’s mouth, tipping it so that he has no choice but to drink the remainder of the potion. 

Sirius flinches violently, cowering, and Regulus realises that he hasn’t seen his brother frightened and helpless like this since they were both children, and their mother was advancing on him with her wand. 

“ Please ,” Sirius begs, his face contorted with fear. “ Please , don’t hurt him, hurt me instead…”

He’s talking about me , Regulus realises suddenly, with a rush of emotion. He thinks he’s trying to protect me. And here Regulus is, feeding him this poison, hurting him. 

For a moment, the temptation to fling the potion back into the basin, to grab his older brother and go back across the lake to the others, is almost overwhelming. But they’re so close to reaching the Horcrux, he reminds himself. This is the reason they’ve come all this way, to take it, to bring the Dark Lord down. They have to keep going. 

“No!” Sirius cries out again, as Regulus forces himself to dip the goblet into the basin again, filling it to the brim with more bright green potion. “Make it stop, make it stop!” 

“Shh,” Regulus soothes, as though he’s comforting a small child. “It’s alright, this will make it stop…”

His self-loathing intensifies impossibly with his lie, as he tips more potion into his brother’s open mouth. Sirius screams, the noise echoing all around the vast cave, across the silent dark water. 

Regulus almost drops the goblet, horror rippling through him; he hasn’t heard his brother scream like that since the night he had hovered helplessly outside the closed door of his father’s office, shrinking into the darkness as his parents walked out of the room and locked Sirius in. The night that Sirius had run away. The night that everything had shattered.

“It hurts!” Sirius screams. “Please… please stop…no more…I can’t!” 

“Sirius, it’s alright, you’re alright!” Regulus cries loudly, trying to drown out his brother’s screams. He can feel his eyes burning with tears now, his hands shaking so badly that he can barely scoop up the sixth goblet of potion; he scarcely even registers that the basin is half-empty now. “Nothing’s happening to you, I swear, you’re safe here, just…just drink…”

Sirius is blindly obeying him, for the first time in his life, drinking desperately as though it’s an antidote that Regulus is offering him - but once the goblet is drained, he sinks to his knees, shaking uncontrollably. 

“Prongs,” he whispers now. “I fucked up, I know I did…he hates me, Prongs…he’s never going to speak to me again…it’s all my fault, I know it is…please tell him, help me, I’ll never, never again…”

“This will help,” Regulus whispers back, tears pouring down his face now, wondering if his brother is still talking about him, his voice cracking as he tips the seventh goblet of potion into his mouth. 

As he forces himself to fill another goblet, his other hand clutching Sirius’s shoulder desperately as though that might somehow keep him anchored to reality - or perhaps just absolve Regulus of his guilt - his brother cowers as though invisible torturers are surrounding him, his flailing hand almost knocking the refilled goblet from Regulus’s hands. 

“Please…please…no more…”

“For god’s sake, Sirius, just drink it, please!” Regulus begs, his voice trembling almost as much as his hands. He doesn’t know how much more of this he can take.

Again, Sirius drinks obediently, even desperately, like a child dying of thirst - but as soon as he finishes, he starts to cry in great heaving sobs, tears streaming down his face.

“Why?” he moans between sobs. “Why are you doing this, Moony? Is it to punish me? But I said I was sorry, I said I was SORRY…PLEASE!” 

Regulus scoops up another goblet and feels the tiniest twinge of relief as it scrapes the bottom of the basin. 

“We’re nearly there, Sirius, just…drink this…” 

He supports his brother’s shoulders and once again, Sirius drains the goblet of potion; Regulus is already refilling it as he begins to scream again, more anguished than ever now. 

“What do you want from me, what do you want? I’ll cut out my heart, I’ll give it to you, if that will make you forgive me, if that will make it stop…just make it stop!!”

“This one will make it stop!” Regulus gasps, praying that this time it’s not a lie. “Just drink this, Sirius, it will be over, all over!”

Sirius gulps it, draining every last drop, and Regulus drops the goblet, staring down into the basin which is finally empty of potion. 

He can’t help but inhale slightly in awe - it’s right there, coiled up. A large golden, oval locket, a serpentine pattern of emeralds creating Slytherin’s mark. 

The Horcrux. 

Hands shaking violently, Regulus takes the fake locket with the note out of his pocket. Heart pounding, he snatches the Horcrux from the basin, throwing the fake down in its place and putting Slytherin’s locket around his neck, dropping it down the front of his shirt. It’s icy cold against his skin - he could almost imagine it has a tiny heartbeat, ticking irregularly alongside the frantic thumping of his own. 

We’ve got it , he thinks, stunned. 

And then Regulus is distracted by a great, rattling gasp behind him that makes his blood run cold. He whips around to see that Sirius has rolled over onto his face, lying there completely still. 

“No!” he cries out, terror clawing at his throat as he flings himself down beside his brother and heaves him over onto his back; Sirius is deathly pale, his eyes closed. 

“Sirius… Sirius !” he pleads, shaking his shoulder desperately. He sounds like a small child himself now. “Rennervate!” he croaks, panic choking him; there’s a flash of red light from his wand. Nothing happens. “Rennervate… Sirius… please…” 

His brother’s eyelids flicker; his heart leaps. 

“Sirius,” he breathes, almost crying with relief. “Are you…”

“Water,” Sirius croaks, his voice feebler than Regulus has ever heard it. 

“Water,” Regulus echoes, “of course…yes…” 

He hastily seizes the goblet he’d dropped. 

“Aguamenti,” he gasps, jabbing at it with his wand. Instantly, the goblet fills with clear water, and he hastens over to Sirius - but as he brings it up so his brother can drink, the water vanishes, leaving the goblet empty. 

“Wait…but…no… Aguamenti!” 

Once more, clear water gleams within the goblet again, but vanishes a moment later. 

“I’m trying, Sirius, I’m trying!” Regulus shouts, crying in earnest now. Sirius is drawing shallow, rattling breaths that sound agonising, and his mind is whirling, spinning out of control in his panic. 

He remembers, then, the next detail of Kreacher’s story, what he’d been forced to do when he’d thought he would die of thirst. 

Fuck. 

But what other choice does he have? 

Desperately, Regulus flings himself over to the edge of the rock, plunging the goblet into the lake and bringing it up full to the brim with icy water. This time, it doesn’t vanish. 

“Sirius - here!” he shouts, lunging forwards and doing his best to tip the water into his mouth.

At the same time, Regulus realises, terror expanding inside him and filling his lungs, that the icy feeling on his other arm isn’t the lingering chill of the water. 

A slimy, marble white hand has gripped him by the wrist - he’s being pulled slowly backwards across the rock. The surface of the lake is no longer mirror-smooth, but churning; everywhere Regulus looks, white heads and hands are emerging, men and women and children are moving towards the rock. 

An army of the dead, rising from the black water. 

“ Petrificus Totalus!” he yells desperately, pointing his wand at the Inferius clutching him; it releases him, falling abruptly back into the water with a splash. 

But many more are climbing onto the rock, bony hands clawing at the slippery surface, blank frosted eyes staring at him, trailing waterlogged rags. 

“Petrificus Totalus!” he yells again. “Impedimenta! Incarcerous!” 

A few of them stumble, a couple bound in ropes, but more are climbing onto the rock behind them. Regulus feels like he’s fallen into one of his childhood nightmares. His mind is blank, with only one thought screaming at him: don’t let them get to Sirius. 

He scrambles clumsily back to his brother, grazing his arm on the rock as he goes. Sirius is still lying on the ground by the basin, stirring only feebly; Regulus grabs his fallen wand, throwing his arms out, trying desperately to shield him.

He can’t die, his mind babbles at him. Not here, not like this. After everything he’s done for you…you can’t let him die.

And then, finally , a clear thought sinks in through the blind fog of panic - and Regulus remembers that there is, after all, a way out. 

“INCENDIO!” he screams, two wands in his hand, concentrating harder than he ever has before. 

His heart nearly bursts with relief as fire erupts through the darkness of the cave; crimson and gold and so bright that it almost dazzles him. The firelight reflects off the lake, bathing them in sudden warmth. A few of the closest Inferi catch alight, going up in flames; others around them flinch back.

“Fabian! Lupin!” Regulus shouts desperately across the water, his hand shaking with the effort to keep the spell going. His own voice, raw with tears and panic, echoes back at him. “Help! Fire! Please! 

For a moment, nothing but silence greets him, and terror catches in his throat as he wonders if the other two just can’t hear him, or if something worse has happened to them…

But the next moment, more firelight flares out across the water, so that the entire cave is illuminated, light and warmth everywhere. 

The Inferi stumble and falter, bumping into each other as they attempt to escape the scarlet and gold flames. Desperately, they surge back towards the dark water.

Panting with the effort of maintaining the spell, Regulus turns to his brother.

“Sirius,” he urges, his voice hoarse, “are you strong enough to transform back? Please? I need you to transform back, now!” 

Sirius blinks and stares up at him, paler than Regulus has ever seen him, his chest rising and falling weakly. A moment later, a large black dog is lying very still in the spot where he’d just been. 

“Thank god,” Regulus breathes. 

Without bothering to be too gentle, he lifts Sirius, one-handed - the dog is much heavier than he’d expected - and throws him clumsily into the little green boat. He hastily unhooks it from the rock and scrambles in after him, utterly exhausted, but still using both their wands to keep the fire spell going, too terrified to stop. 

The boat begins to move smoothly back towards the opposite bank, the firelight making bright, dancing reflections on the water. It seems that the Inferi swarming below don’t dare to resurface. 

Regulus nearly weeps with relief as the boat finally reaches the opposite bank with a small bump. Lupin and Fabian are both standing there, pale faces illuminated in the fire pouring from their wands. He stumbles onto the bank, gasping, finally letting his wand hand fall so that the flames from both his and Sirius’s wands vanish. He’s never felt so drained in his life. 

“Oh my god…” Lupin breathes, the fire from his wand abruptly stuttering out too. His eyes widen with terror as he stares over Regulus’s shoulder. The black dog is still slumped in the boat, completely still. 

“He’ll be alright!” Regulus tells him hastily, not entirely sure that he believes it himself. He hates the pleading note in his voice. “It was…it was his idea, to drink all of that stupid potion by himself, I swear!” His voice breaks. “I told him I would do it, but he was just…he was being a stubborn dick as usual, you know how he gets, Lupin, and…”

But Lupin glares at him, and he trails off, looking down at the ground. The scarred man walks over to the boat and lifts the dog into his arms, much more careful and gentle with Sirius than Regulus had been, cradling him. Then he turns abruptly back to Regulus, who steps back a little in alarm. 

“You got it, I assume?” he asks. “The locket?”

“What?” Regulus replies, dazed. He’s almost forgotten what they went through all of that for. “Oh..yes, it’s right here.” He tugs lightly on the chain around his neck. Lupin glances down at it briefly and nods. 

“Good. I’m glad,” he says, his voice very quiet, staring at Regulus with the coldest, most frightening expression he’s ever seen on the other man’s face. “But if he’s not bouncing around and back to being a stubborn dick within the next few hours, then I don’t care how many Horcruxes you’ve collected, I will kill you myself, Regulus. Do you understand me?” 

Regulus just nods, staring down at the ground. He can feel Fabian’s concerned gaze, but he doesn’t look up at him. He knows he doesn’t deserve his sympathy.

“Good,” says Lupin shortly, with a nod of his own. 

He turns around, still clutching the black dog in his arms; when he finds himself facing just a blank wall of rock, he doesn’t say anything, but gives it a vicious kick, breathing hard.

“Here,” Regulus says hastily, hurrying forwards. “I can get us through, I got cut on the rock…” 

He wipes his grazed forearm on the stone; having received its tribute of blood, the archway reopens instantly. Lupin doesn’t offer a word of thanks, but just carries Sirius through it without looking at him. Regulus just stands there for a moment, shaking with the weight of…everything. He comes back to himself a little when Fabian nudges him. 

“C’mon,” he whispers, tugging him gently through the archway before it closes again. 

They’re standing in the small antechamber again, grey water churning deafeningly through the slit in the rock face. Regulus is so exhausted that he almost sits down and starts crying at the prospect of having to swim again. 

Fabian glances at him guiltily. 

“I’d better help Remus,” he says awkwardly, “dunno if he can manage swimming through with a bloody great dog on his own.” Regulus nods. “Will you be…”

“I’m fine, Fabian,” he says sharply. He can’t bear the other man’s kindness, right now. 

The redhead nods, not looking very convinced. He reaches out to squeeze his shoulder gently, before hurrying off after Lupin.

Regulus takes a deep breath and closes his eyes, willing himself not to shatter, before sliding into the icy sea water. 

He shudders, gasping; he’d forgotten just how cold it was. He kicks out fiercely, his lungs already screaming at him in protest, his clothes already waterlogged, weighing him down. 

He struggles, forcing himself to push on. Just keep going , he tells himself. Only a bit further. He kicks out, managing to push through for a few minutes, trying to emulate the strong breaststroke he’d seen Fabian and Sirius doing earlier. Sirius. 

He closes his eyes, and immediately he’s back in the cave again, hearing his brother’s screams, seeing his pale face, the dead men and women rising from the dark water imprinted on his eyelids. Regulus had been sure they’d already escaped, but here he is again, struggling to keep his head above the water. It’s so cold, and he’s so tired…

What if he just stopped swimming? Stopped trying to resist, simply relaxed into the icy water and let it drag him under, let himself rest? After all, the Dark Lord will kill him anyway when he finds what he’s done, and clearly nobody in the Order actually likes him or trusts him…would anybody actually miss him?

Regulus lets out a long sigh, and stops kicking, making himself completely still. 

But then, out of nowhere, a strong, warm pair of arms encircles him, tugging him forwards, pulling his face further from the icy water.

“Oh no you bloody don’t,” a familiar voice growls in his ear. Fabian. 

His heart gives a tiny kick of relief in his chest. Regulus is much too tired to struggle against the broader man, so he lets himself lean against him. A hand brushes against his neck; he wonders what the redhead is doing, and then realises vaguely that the icy pressure that was weighing down on his chest has vanished. Fabian must have lifted the Horcrux over his head. 

Regulus closes his eyes again, letting Fabian pull him along, kicking only feebly to help him. 

Finally, he feels himself being lifted out of the water. Fabian mutters something; apparently a drying spell, as Regulus immediately feels as though he’s in front of a blazing fire. He sinks down to the ground, shaking from head to foot. 

After a moment, he forces himself to open his eyes. They’re back on the outcrop of dark rock where Kreacher had brought them, grey waves crashing relentlessly around them. Looking around, he sees no sign of Sirius and Lupin. 

“Where are the others?” he croaks.

“Remus already took Sirius back to their flat.” 

“Oh.” He searches for something else to say. “Thought you went to help Lupin?” 

“I did,” Fabian replies stiffly. “And then I doubled back to help you…bloody lucky I did, wasn’t it?” 

It’s strange to hear such rage in Fabian Prewett’s voice. Regulus looks up warily, to see that Fabian is glaring at him furiously, arms crossed over his chest, a muscle twitching in his jaw. 

“You want to tell me what the hell that was, Regulus?” 

He sighs.

“I’m tired,” he mutters, shrugging. “And, like Sirius said before, I’m not that strong a swimmer…”

“Bullshit,” says Fabian, his voice cracking slightly. 

Regulus blinks up at him, surprised to realise that it’s not just fury suffusing his handsome features - his blue eyes are flickering with fear and worry. Regulus swallows, his throat suddenly tight. 

“I…I should have drunk that potion,” he whispers, trying to force back the tears. “ I should have drunk it, Fabian, I shouldn’t have let Sirius…Those two are never going to forgive me. They shouldn’t forgive me. Nobody should.” 

Fabian studies him, his face finally softening. Slowly, he crouches down until he’s eye level with Regulus, sitting on the ground. 

“Hey,” he murmurs, expression much more familiar now as he reaches out to place a gentle hand on his shoulder. His warm touch seems to soak into Regulus’s skin through his clothes, and it’s far more comforting than he’s willing to admit. “It was not your fault. Like you said earlier, Sirius is a stubborn dick. Everyone knows that.” 

Regulus laughs a little at that, even though he doesn’t want to. Fabian grins back at him, looking immensely relieved. Regulus feels something spark into life in his chest. Something hopeful. 

Fabian gets back to his feet, holding out his hand to Regulus to pull him up too. 

“Where are we going?” he asks.

“I’m taking you back to Sirius and Remus’s flat,” Fabian responds. “Sirius will be worried sick about you - not that he’d ever admit it, mind. Besides, you need to rest.”

Regulus grimaces, but he sees that there’s no point in arguing with him. 

“Oh, and by the way,” he adds, “I’m not going to call you ‘just Regulus’ any more.” 

“What? Why not?” Regulus asks, confused.

“Because you’re not ‘just’ Regulus,” the redhead answers quietly. “You’re not ‘just’ anything.” 

‘...Oh,” he replies lamely, feeling strangely winded. 

“C’mon, I’ll Side-Along you, you’re exhausted,” Fabian grins at him, determinedly casual again as he holds out his arm. Regulus hesitates.

“Fabian?” he asks quietly.

“Yeah?” 

“Please don’t…don’t tell the others. Especially not my brother.” 

Fabian’s bright blue eyes flicker over his face.

“I won’t,” he murmurs. “I promise.”

Regulus gives him a small, grateful smile.

“Thank you.” 

He reaches out to clutch the arm that Fabian is proffering. The redhead turns on the spot, and the salty sea air, the towering cliff and the grey waves all vanish.

A moment later, the two of them are standing once again in the middle of Sirius and Remus’s small living room; Regulus awkwardly lets go of Fabian’s arm, stepping away to give him more space. 

Glancing around, Regulus immediately feels guilt clogging his throat again. Sirius is lying on the sofa opposite, still in dog form; evidently, he’s still not feeling strong enough to transform back. Lupin has lit the lamps; he’s tucking a blanket around the black dog with infinite care.

He looks up at the sound of the other two Apparating, and glares at Regulus. 

“Don’t remember saying you could both come back with us, Fab,” he says pointedly. Regulus winces. 

“Remus,” says Fabian, his tone much sterner than usual. “Stop it.” 

Lupin looks at him, surprise written across his face for a moment; but to Regulus’s relief, he makes no further comment, but simply nods and turns back to Sirius. 

Regulus sinks down into an armchair, trembling a little, watching Lupin taking care of his brother, placing a cushion gently under the dog. There’s so much love in his eyes that Regulus looks away awkwardly. 

The living room is almost completely silent; Regulus looks up at Fabian, who’s hovering next to his chair.

“Right,” Fabian sighs, rubbing his forehead wearily. “Well, I should probably go check on -”

But he’s cut off as a familiar silver phoenix soars through the open window of the flat. The three of them cry out in alarm, though the black dog still doesn’t stir. 

Regulus tries to swallow, his heart lodged in his throat again. God, what does Dumbledore want now?

“I regret to say that there was an ambush lying in wait for the people on guard duty tonight,” the Patronus announces, that deep, familiar voice echoing through the little flat. “I am so, so sorry, Fabian. Dorcas and Gideon have both been killed. I strongly recommend that you go to the Burrow at once - I am about to inform Molly. I have a feeling that she might be needing you.”