promises, oceans deep

31st October, 1979

“Just drink it, you big baby.”

“It’s gonna taste like shit.”

“You ingested a whole basin full of poison less than a week ago, Sirius, I think you can handle this.”

Sirius frowns over at his brother, reluctantly agreeing that yes, he can probably handle this , “Just know that I’m not happy about it.”

Regulus rolls his eyes, tipping his head back to rest on the back of the armchair, “I wouldn't expect anything less.”

Sirius takes in a deep breath, staring warily at the vial of Polyjuice that Regulus has presented him with only moments ago. Merlin, he just really can’t get over the fact that there’s teeth in there. He holds back a gag. 

“ Sirius , we’re on a time limit, here!” Regulus huffs, snapping upright in his chair, “If you don’t do it, I will!”

No, he won’t. After much debate, it was decided that only Sirius could pose as Bellatrix - due to the fact that it would be exceedingly odd if he were to make a public appearance with his least favourite, most crazy cousin. So, no, Regulus would not be drinking the potion himself.

Though the impatient look in his eyes has Sirius clutching the vial tighter to his chest.

“Just…give me a second. Let me count myself down or something.” Sirius swirls the vial slowly, wrinkling his nose at the pungent scent. 

A long moment passes.

“I've noticed that you're not counting yourself down like you said you would-”

Sirius downs the potion. 

“Finally.” Regulus slumps down into the armchair again, though his eyes are sharply observing Sirius for any signs of transformation. 

“I feel like it’s not worki-”

All at once, Sirius feels his skin shift and remould. The sensation is not unlike his Padfoot transformation, though turning into a different person is certainly more of a mindfuck than simply changing species. The world feels slightly off-balance - almost normal but not quite right .

Regulus is staring at him with thinly-veiled horror, “Merlin, that’s weird.”

“I think… I think I’m taller , now?” Sirius breathes, holding out his hands to examine the bony, feminine fingers that have replaced his own, “Since when is Bellatrix taller than me?”

Regulus rolls his eyes, looking like he can barely stop the words shut up from escaping his pursed lips, “Focus. We should have a good few hours before the potion wears off but we’re better safe than sorry.”

Sirius nods firmly because he actually is focused, thank you very much. This next Horcrux is going to be much harder to get than the last one, if only because this one requires them going out in public for the first time. If a single thing goes wrong, their plan is exposed and Voldemort will come for them. So, yes, Sirius is focused. 

“Well, then. We should probably get going, shouldn't we?”

-

The Black brothers arrive in Diagon Alley, pressing against the wall of a dingy alleyway. The morning air is frigid, misting with every exhale that leaves Sirius’ lips. The task suddenly seems a lot more real.

At his side, Regulus is casting a Notice-Me-Not charm over himself, muttering the spell under his breath. While Bellatrix and Regulus spending time together in public wouldn’t necessarily be cause for confusion, it's still safer that his identity remains a vague blur in the minds of the goblins at Gringotts. They can’t risk suspicion from Riddle.

Regulus completes the charm and turns to his brother, brows drawn in determination, “Are you ready? We only get one shot at this.”

Sirius grins. Impersonating his least favourite cousin in a high-stakes heist where one wrong move could get them killed? Oh, he was born ready. 

Flashing a much smaller returning smile, Regulus gestures down the alley for Sirius to lead the way.

-

Sirius has only been to Gringotts a few times, mainly when he was younger. His patchy memory does no justice to the magnificent beauty of the bank. He can barely hold in his gasp as he pushes through the high doors, Regulus at his side. 

Walking into the bank as Bellatrix is just as exhilarating as it is terrifying. The few goblins that look up from their desks gasp in fear, quickly looking away as soon as they make eye contact.

Oh yeah, Sirius can definitely work with this. 

He struts confidently to the front desk of the bank, relishing in the sharp, threatening noise of his heeled footsteps. 

When the goblin at the desk fails to look up at his approach, Sirius lets out a sharp cough that would put his own mother to shame. The goblin slowly raises his head, eyes slightly widening at the sight of Bellatrix Lestrange in front of him. Thankfully, his eyes almost completely skim over Regulus’ still figure. 

“Madam Lestrange!” The goblin smiles stiffly, “What can I help you with this morning?”

Sirius fixes him with a critical look, “I’m here to access my vault. Clearly.”

The goblin clears his throat, embarrassed, “Yes, of course. Well, first we must confirm your identity to-”

“Confirm my identity?” Sirius repeats, aghast, “Am I not stood right in front of you? What could possibly need checking?!”

“Well, yes but for security reasons, we must-”

“Do I not look myself?” Sirius snarls, trying to reach that pitch that only dogs can hear - the one Bellatrix has perfected, “Do I look different? Have I gained weight?”

“No, no, Madam Lestr-”

“Are you calling me fat ?!”

“ What ? Of course no-”

“You’re telling me , a respected patron, that I am too ugly and fat to enter your establishment?” Sirius turns to look for an invisible manager, “In all my years, I've never encountered such disrespect -” 

A second goblin comes to the rescue of his colleague, a faux grin on his wrinkled face, “You can come right through, Madam Lestrange. Apologies for any insult.”

Sirius straightens out his skirt, raising an arched eyebrow, “I should think so.”

The two goblins whisper furiously to eachother for a long moment, before turning back to the brothers and gesturing for them to follow the second goblin. 

As he guides them through the bank, Regulus catches Sirius’ eye to fix him with a bewildered expression, silently asking how the hell did that work?

Sirius throws a smug shrug his brother’s way before resuming his impression of Bellatrix’s nonchalant yet simultaneously intense demeanour. What a fun game!

The brothers are led through endless winding hallways, deeper and deeper into the bank. Sirius counts at least four staircases throughout their journey before the goblin leads them through a tall, gaping doorway. 

They’re met with a deep, dark cavern - home to a singular cart that rests on winding, endless tracks that lead into the depths of the darkness. 

“If you and your, uh, guest could just climb into the cart?” the goblin gestures to it with a stiff smile on his face, still slightly too wary to make eye contact with the pair.

Sirius has half the mind to refuse before remembering that he is Bellatrix right now, and that Bellatrix has made this journey many times before. So, he makes his way onto the cart, ignoring every survival instinct in him telling him to run as far away from this death-trap as possible. 

He looks up to catch Regulus barely resisting smacking the goblins hand away as it reaches to assist him into his seat. Sirius has to bite back a snicker, the sight of his brother’s curled lip all too familiar. It’s an expression reminiscent of a tiny, feral cat.

Regulus glares at him, clearly seeing the teasing insults racing through his brother’s mind.

Without warning, the cart launches into motion, tearing down the tracks with an eye-wateringly fast speed. Sirius can barely stop himself from gripping onto Regulus’ arm for safety - forcing himself to continue to echo Bellatrix’s immunity to fear. Regulus is stiff against his side, clearly resisting doing the same. The goblin behind them cackles with glee. Sirius wants to drop-kick him into the abyss.

After a few minutes of hurtling at deadly speed through the cavern, a distant glow catches Sirius’ eye. As they draw closer, the glow turns into a colossal, vertical waterfall that crashes onto the tracks. He turns to Regulus. Shit. No one said anything about a magical waterfall. 

The cart hurtles closer to the waterfall. Helplessly, Sirius braces himself, closing his eyes as the water crashes over their heads.

Immediately, he can feel his disguise wear off. His hair shrinks to sit at his shoulders instead of his waist, while his body shifts back to its regular, lean shape. Shit.

After a few more agonising moments, the cart screeches to a stop right in the middle of the tracks. Sirius has enough time to turn in confusion before the three of them are plummeting into the rocks below. Just as he’s sure he’s about to meet his head, he hears Regulus’ voice echo clearly throughout the cavern, “MOLLIARE! ”

Thank Merlin for Regulus’ quick thinking. Sirius lands gently on the floor, taking the time to shake out his dripping hair. Regulus curls his lip, shielding his scarred face from the flying droplets. 

Sirius looks down at himself, muttering a despondent, “My Halloween costume…”

“Shut up, Sirius.”

The goblin mutters to himself as he brushes off his suit, yet to look up and see two people who are certainly not Bellatrix Lestrange. He raises his head and his mouth drops open at the sight of them, “What is the meaning of this? Impersonating a patron like this? I ought to call the Aurors as soon as I get my hands on-”

He crumples to the ground. 

“Sirius! He was our way in!” Regulus squawks, gripping his hair in frustration.

Sirius shakes out his hand, sore from wacking the goblin on the head, “I’m sorry, I panicked! He was going to call the Aurors!”

Regulus closed his eyes, hand reaching to pinch the bridge of his nose. He takes a deep breath, “It’s fine, we’ll just have to carry him. We just need his handprint anyway.”

Sirius nods and reaches down in preparation to lift the goblin up into his arms. He pauses when he sees that his brother hasn’t moved, “Aren’t you going to help?”

“Sorry, am I the one who went rogue and decided to beat up our only way in?” Regulus snaps, brows disappearing into his hair, “No, I don’t believe I am. You knocked him out, you’re carrying him. Come on.”

With that, he stalks off into the dark. Sirius lets out a groan before hoisting the goblin into his arms. How romantic. He begins to trek after his brother.

He finds Regulus stopped outside what must be Bellatrix’s vault, tapping his foot impatiently, “Merlin, could you have taken any longer?”

“I’m carrying a whole person, Regulus! Forgive me if I’m a little slower than usual!” Sirius snaps, though nearly overbalancing and falling removes any level of intimidation he could have had.

Regulus simply rolls his eyes and gestures to the gate in front of them, “Place his hand here, that should unlock it. And then we can just, I don't know, dump him here until we need to leave.”

Sirius follows Regulus’ instructions, marvelling at the way the gate opens up in front of them. He gently props the goblin up against the cave wall and follows his brother inside.

Before entering, Regulus turns and clutches at Sirius’ arm, “Sirius. Do not touch anything that isn’t the Goblet. Okay? Say okay.”

“Okay.” Sirius huffs. He’s not a complete idiot. 

-

“Sirius, you’re a complete idiot!” Regulus shouts, hands clutching the Horcrux close to his chest.

“I’m sorry, it’s not my fault! The thing fell on me!” Sirius yells back, desperately trying to claw his way through the frequently multiplying pieces of finery.

The thing in question is a golden bracelet that had tumbled off of one of the piles of treasure and landed on Sirius' shoulder. Which had hurt, by the way!

Of course, what hurts more is a billion of those same bracelets raining down on you as you desperately try to crawl away. Which is what's currently happening, if you were wondering. 

“Okay, just try to - ow, fuck - try to just climb out of here.” Regulus calls, in the distance, “Follow my voice, I was closer to the exit.”

Sirius obliges, trying to follow Regulus’ calls until he spots a mop of black hair in all the gold. The brothers meet, falling into eachother as they scramble through all multiplying treasure. Eventually, they reach the exit - hauling themselves out of the piles of gold and onto the damp cave floor.

The pair of them can only lay there for a long moment, chests heaving in exertion. Eventually Sirius finds the breath to ask, “Are you okay?”

“Yep.” Comes the strained reply, “Just a few bumps and bruises.”

Sirius nods in acceptance, letting his eyes briefly slide closed. To his left, he can hear Regulus sit up and begin to pack the Goblet away into his backpack. Thank Merlin, that thing had been starting to give him a headache. 

A few silent moments pass before Sirius feels the tip of a shoe nudge his ribs, “Get up, we need to get out of here. I’m not sure what measures they have in place for break-ins.”

Groaning, Sirius hauls himself upright. A few feet away the goblin begins to moan and shift slightly. Sirius’ eyes widen in panic as the goblin moves to look right at him. Before the thing can even begin to speak, he hisses out a rushed, “Imperio.”

Regulus lets out a half-hearted noise of protest, sealing his bag, “At least you didn’t knock his brains out this time.”

“Okay, you’re making this sound very violent when it was really just a-”

“Focus, you have a cursed goblin to look after.”

“Shit, you’re right.” Sirius sucked in a breath, turning back to the vacant, compliant goblin, “Okay, uh. Gobli- uh, Sir? Take us back to the bank, please. Now.”

The goblin - whose name Sirius should really know by now - nods and smiles, eyes milky and blank. He leads the brothers back over to the cart.

“Oh, brilliant, another go on the death-trap.” Regulus mutters, this time taking a seat first. His hands curl protectively around his bag. Sirius sits down beside him, grimacing.

The ride back isn’t as unpleasant as the ride there, now that Sirius knows to expect to travel at a speed that could probably tear his face off. This time, it's more of a begrudging fear than an all-consuming terror. The paleness of Regulus’ face would disagree, however, so Sirius does not voice his opinions. 

The cart finally stops back in the cavern they started in, the light of the bank seeping through the doorway. Sirius climbs out on shaky legs, “Terrible, inefficient way to travel, by the way. I will not be using your services again, thank you.”

“Sirius, shut up.” Regulus grumbles, climbing out behind him. He turns to the goblin, “He’s right, though. This is an incredibly inefficient establishment.”

As the goblin leads them back through the bank, Sirius begins to get nervous. Without his disguise, he feels very exposed, “How the hell do we get out of here without being recognised?”

“Just relax, I have a plan.” Regulus whispers back, pulling out his wand.

Trusting his brother, Sirius just focuses on taking deep breaths as they near the main hall of the bank. When they’re close enough to hear the chatter of the other goblins working, Regulus stops in front of him, “Okay, when I say go, I need you to just close your eyes and sprint outside. It's a straight path, we should be fine. Okay?”

“But what are you-”

“Just say okay.”

“Okay. I trust you.”

Regulus freezes for a moment, startled, before nodding firmly. He straightens and walks confidently towards the hall. Shit, okay. Sirius follows. 

As soon as they pass the threshold of the hall, Regulus gives him a sharp shove and yells, “Sirius, go! LUMOS SOLEM!”

Sirius slams his eyes shut and sprints, hoping his memory serves him well as he attempts to navigate his way to the exit. Through his eyelids, he sees a great bright light filling his vision. Despite his eyes being shut, the brightness of it stings. Hands slam into his back, once more, pushing him through the solid doors that lead into Gringotts.

His brother’s voice sounds in his ears, “Okay, you can open your eyes.”

Sirius does and turns to look at his brother. The brightness of a few moments ago has turned Diagon Alley into a dim, grey blur, “What the hell was that?”

Regulus smirks, pulling him into a run as they tear away from the bank, “It was an illumination charm. A really fucking good one, actually. Everyone in there was too blinded by the light to see who we were, so we should be safe.” 

Sirius wonders distantly when his little brother will stop impressing him. Of course, he can never voice that thought and give Regulus that kind of ego, but still. He can’t quite work out when his little brother grew up without him.

Regulus pulls them into an alley, moving his bag so that it’s grasped securely in his arms, “Okay, let's get this thing out of here.”

It’s then that Sirius registers the task that they had just completed. Holy shit, they actually have the Second Horcrux!

Two down, only three to go.