Polyjuice Potion | Sebastian Sallow x Reader
The Polyjuice Potion had worked—perhaps a little too well.
You examined your reflection in the polished surface of a nearby suit of armor, recognizing yourself as Phineas Nigellus Black, the ever-ill-tempered, egotistical headmaster of Hogwarts. The pinched expression, the stiff posture, the perpetual air of disdain—it was all there. Even the scent of expensive cologne and the faintest trace of ink clung to the borrowed robes.
A smirk curled at your lips. Oh, this was going to be fun.
With an exaggerated gait befitting your new persona, you made your way through the halls, relishing the way students shrank back at your approach. Their hushed whispers and wary glances only fed your growing amusement.
The plan had been simple: borrow the headmaster’s form, strut around the castle unchecked, and slip into the Restricted Section of the library to retrieve a book you and Sebastian needed for your latest round of mischief. But when you happened to spot him lounging against a pillar in the Transfiguration Courtyard, casually chatting with a nervous-looking first-year, an even better idea formed in your mind.
You and Sebastian were newly courting, a fact that thrilled and terrified you in equal measure. There had always been something between you—something charged, something exhilarating—but now? Now your nightly post-curfew meetings had tipped over into the territory of... inappropriate. From late-night rendezvous in the Undercroft to the hours spent whispering in hushed tones behind stacks of books and the absolutely improper things he had said to you just last night beneath the Forbidden Forest’s canopy, it was a miracle you hadn’t already been caught.
And seeing him now, with your identity hidden, provided the perfect opportunity to push his buttons—and perhaps, make him think you had been caught in the act, after all.
With deliberate, booming steps, you approached, clearing your throat with all the authority you could muster.
“Mr. Sallow.”
Sebastian stiffened immediately, snapping to attention. The first-year beside him went rigid, then bolted without a word, leaving Sebastian standing alone, blinking up at you—well, at Professor Black—with rapidly dawning concern.
“Professor,” he greeted, schooling his features into careful neutrality.
You clasped your hands behind your back, surveying him with the kind of imperious air you imagined the real headmaster would use. “I have been informed of certain… late-night escapades involving you and our new fifth-year student.”
Sebastian’s expression flickered—so fast that most wouldn’t have caught it. A tightening of his jaw. A twitch of his fingers.
But you did.
“I don’t know what you mean, sir,” he said smoothly, ever the picture of a model student.
“Oh, don’t be coy, Mr. Sallow.” You tilted your chin, enjoying the way his confidence wavered. “I am well aware of the frequent, shall we say, disappearances you and your companion have orchestrated.”
Sebastian blinked. Then, to your delight, his composure cracked just a fraction more. “Disappearances?”
“Yes.” You let the word drag, savoring it. “Discreet meetings. Secluded alcoves. Library corners far removed from prying eyes.” You paused for effect. “Surely, you don’t think the faculty are so blind?”
Sebastian was staring at you now, eyes darting around as if trying to determine just how much you knew—or rather, how much ‘Black’ knew. The corners of his ears were already turning pink.
You pressed on. “One might begin to wonder if these outings are of an… inappropriate nature.”
Sebastian choked.
Actually choked.
His composure—so carefully maintained, so effortlessly wielded in the face of authority—shattered like glass. He coughed violently, eyes widening in what could only be described as pure, undiluted horror.
“Inappropriate?” he managed, voice an octave higher than usual. “Sir, I—”
You held up a hand, cutting him off. “Now, now, Mr. Sallow, let us not be hasty in our denials.” You paced in a slow circle around him, watching the way his shoulders squared, the way his fingers twitched at his sides. “If, hypothetically, a situation were to arise—say, one resulting in an unexpected addition to the Hogwarts population—well, naturally, a marriage would be required.”
Sebastian’s mouth fell open.
“You mean a— a baby?!” he sputtered, looking positively scandalized. “What—no! That’s not—Sir, you have completely misunderstood—”
“I do hope so, for your sake.” You exhaled, shaking your head in mock disappointment. “It would be rather tedious, wouldn’t it? Organizing a ceremony, ensuring the Ministry is properly notified… And of course, the matter of parental consent.” You tutted. “Although, given your companion's… unfortunate lack of proper guardianship, I suppose we’d have to settle the matter internally. A pity, really.”
Sebastian’s ears were no longer pink; they were burning red.
“Sir,” he tried, his voice betraying the barest hint of a waver, “with all due respect, I—”
“Oh, but I must admit, the match does seem fitting.” You clasped your hands, peering down at him as if contemplating it seriously. “Our new fifth-year has certainly reined in that reckless streak of yours. A strong-willed partner to temper your unfortunate disregard for authority.” You sighed dramatically. “Perhaps it is not such a poor idea after all.”
Sebastian looked about two seconds from passing out. His mouth opened and closed, searching for a response but clearly coming up short. He was no doubt replaying every single one of your late-night meetings in his mind, tallying up just how scandalous they must seem from an outsider’s perspective.
You had never seen him so utterly speechless.
“Sir, I assure you, we are not—”
You hummed, tilting your head. “Not yet, perhaps.” Then, as if just coming to a realization, you gasped. “Or is it that you wish it were so?”
Sebastian made an awful noise—somewhere between a strangled yelp and a groan of agony. His hands twitched uselessly at his sides, like he was caught between gesturing wildly in protest and gripping his own hair in frustration.
“Sir—”
"What is it, Sallow? Spit it out, will you."
Sebastian swallowed hard, his usual bravado entirely abandoned. "Sir, I—this is—it's not what you think!"
You raised a single, unimpressed eyebrow. "Oh? Enlighten me, then. What exactly do you think I think?"
Sebastian floundered, his mouth opening and closing like a fish gasping for air. "We—we were just studying!"
You exhaled heavily, as though exhausted by the sheer absurdity of his excuse. "Studying?" you echoed, dryly. "In the dead of night? In hidden corners of the castle? With your hands where, exactly?"
Sebastian made another strangled noise, looking truly panicked now. You almost felt bad for him.
Almost.
You bit the inside of your cheek to keep from laughing. He had no idea. Absolutely no clue. And it was delicious.
"Sir," he finally managed, voice cracking just a little. "I swear on Merlin’s grave, I have never—my hands have never—!"
Liar.
"Mmm." You narrowed your eyes at him, pretending to consider his words. "So you deny any inappropriate conduct with our new student? Any late-night whispers? Any—"
A voice rang out from behind you.
"Professor Black?"
You turned sharply on your heel, schooling your features into the most severe, disapproving expression you could muster. Ominis Gaunt stood a few paces away, his wand held aloft, his pale eyes blinking as he gauged the situation. His usual neutrality was in place, but you knew him well enough to detect the faint exasperation lingering beneath the surface.
As if he were already wondering what the hell Sebastian had done this time.
"Ah, Mr. Gaunt," you greeted, letting the headmaster’s usual tone of clipped condescension seep into your voice. "Excellent timing. I was just having a most illuminating discussion with your dear friend."
Ominis tilted his head ever so slightly, expression betraying a flicker of curiosity. "Sir?"
Sebastian, still reeling from your interrogation, turned to Ominis with wide, pleading eyes. The look clearly screamed: Help me.
You clasped your hands behind your back and resumed your slow, authoritative pacing. "Tell me, Mr. Gaunt, are you aware of your friend’s nightly disappearances with our newest fifth-year?"
Ominis frowned slightly. "I'm afraid I don't know what you mean, Headmaster."
You hummed, turning to regard him with a sharp, scrutinizing gaze. "Is that so? And yet, I have been informed that Mr. Sallow has been... rather indiscreet in his late-night activities with her."
Sebastian choked again, making another strangled sound of distress. Ominis, for his part, merely exhaled through his nose, looking deeply unimpressed. "Sir, I can assure you, whatever you've heard has been exaggerated."
"Oh?" You arched a brow. "So you deny that Mr. Sallow has been sneaking about the castle at all hours, engaging in clandestine meetings?"
Ominis remained impassive. "Sebastian has always been prone to wandering, sir. It’s hardly a new development."
Sebastian latched onto that defense like a lifeline. "Exactly! I just—wander. Aimlessly. Like a—like a ghost!"
Ominis sighed. "Not helping, Sebastian."
You clasped your chin in mock contemplation, as if seriously weighing their words. "I see. And if I were to question our new fifth-year about these wandering excursions, would they give me the same answer?"
Sebastian blanched. Ominis, however, remained eerily calm.
"Undoubtedly," Ominis said smoothly. "And, if I may be so bold, sir, surely the Headmaster has far more pressing matters to concern himself with than the idle movements of two students?"
You narrowed your eyes at him. Clever. Too clever. Ominis knew how to handle authority far too well.
But you weren’t done yet.
You sighed heavily, shaking your head. "Mr. Gaunt, as Headmaster it is my duty to ensure the propriety of all student conduct—especially when it comes to matters of… courtship.”
Sebastian, who had been clinging to Ominis' defense like a drowning man to driftwood, practically flinched at the word.
“Sir, we’re—there’s no—” he croaked.
You cut him off with a sharp wave of your hand, shifting your gaze back to Ominis, whose composed expression now held the barest trace of tension. “Surely, Mr. Gaunt, you, of all people, can appreciate the need for… structure, when it comes to matters of the heart. A proper match. A respectable arrangement.” You sighed, feigning concern. “But alas, young love is so often reckless. Thoughtless. Irresponsible.” You clasped your hands behind your back and shook your head gravely. “Which is why I fear Mr. Sallow is on course to... how shall I say it? Ruin his own future prospects.”
Sebastian, who had already been pale, seemed to turn an even more ghostly shade. “Sir, I—I don’t understand.”
“Oh, but it is quite simple, Mr. Sallow,” you continued smoothly. “Should a scandal arise—an unfortunate circumstance, let’s say—there would be consequences. A proper course of action would have to be taken.”
Sebastian’s eyes flickered wildly between you and Ominis, looking more and more like a cornered animal.
Ominis, who had been handling this entire exchange with relative poise, finally faltered. “Sir, surely—”
“Yes, yes, I know,” you interrupted, waving a hand in exasperation. “You’ll both insist that nothing untoward has occurred. But I must consider appearances, Mr. Gaunt. And if Hogwarts were to find itself at the center of an improper affair, well, we would have no choice but to ensure all parties involved were secured in a respectable manner.”
Sebastian made a sound so strangled it barely qualified as human.
Ominis, for the first time, looked genuinely speechless. His mouth opened slightly, then closed again as though he had completely lost the ability to formulate words.
You clasped your hands behind your back, nodding in a manner you hoped conveyed utmost seriousness. “Yes, yes. A proper arrangement. Ensuring the integrity of all involved parties.” You let the silence stretch, watching as Sebastian struggled to form a coherent response.
“Sir, that is—” Sebastian finally managed, his voice cracking. “That’s completely unnecessary! I assure you, we have done nothing inappropriate!”
“Oh?” You arched a brow, unimpressed. “So you deny any late-night rendezvous? Any secluded meetings?”
Sebastian groaned, dragging his hands down his face. “I—yes, I mean, no! I mean—we weren’t—oh, for Merlin’s sake!”
Ominis, ever the composed one, finally seemed to regain his ability to speak. “Sir, if I may, I truly do not believe this warrants such drastic measures.”
You hummed, considering. “Perhaps. But one cannot be too careful. The reputation of this institution, and our new fifth year, is at stake.” You turned a sharp gaze to Sebastian. “You do care about your companion’s reputation, don’t you, Mr. Sallow?”
Sebastian looked like he wanted the ground to swallow him whole. “Of course I do!”
“Then it is settled,” you said with finality. “Should any… unfortunate rumors arise, we will be prepared to handle the situation appropriately.”
Sebastian groaned again, looking pleadingly at Ominis, who, for once, had no retort prepared. He merely rubbed his temple, looking as though he too wished to vanish from existence.
With that, you turned on your heel, sweeping away with the same imperious air Phineas Nigellus Black was known for, leaving behind a thoroughly scandalized Sebastian Sallow and an utterly exasperated Ominis Gaunt.
And the second you were out of sight, you bolted, biting down hard on your knuckles to keep from cackling out loud.
Oh, that had been worth every single second.
Sebastian Sallow was going to die.
He was sure of it. Whether by expulsion, an arranged marriage, or sheer embarrassment, his demise was imminent.
The rest of the day had been a blur. He barely absorbed a word of his lectures, nearly set his robes on fire in Potions, and had been so lost in thought at lunch that he nearly took a bite out of his goblet instead of his sandwich.
He was spiraling.
He replayed the conversation with Black over and over, trying to decide which part had been the most damning. The secluded alcoves? The suggestion of a scandal? The casual mention of a baby?!
But the worst part—the part that made his stomach twist itself into impossible knots—was the marriage comment.
A proper arrangement.Ensuring the integrity of all involved parties.
Sebastian could barely breathe just thinking about it. Would Black actually force him into it? Could he? He still wasn’t sure what the school’s policies were when it came to these things.
And the worst part—the absolute worst part—was that he couldn’t even properly deny Black’s accusations.
Because you had been sneaking off together. And it had been improper. Very improper.
Sebastian ran a hand down his face.
Merlin’s bloody beard.
What if Black had proof?
Sebastian’s brain short-circuited so violently at the thought that he nearly tripped over his own feet.
No. Absolutely not. He wasn’t ready to even think about that.
Sebastian needed to talk to you. Immediately.
You were the only other person involved in this mess—aside from the bloody headmaster—which meant you were his only hope of figuring out how deep this disaster went.
Did Black speak to you? Did he give you the same accusations? Did he mention marriage?!
Sebastian stormed through the halls, half-aware of students and portraits giving him odd looks as he passed. His usual easygoing confidence was nowhere to be found. He was on a mission.
When he finally spotted you sitting in the Great Hall, completely at ease, not a single ounce of concern on your face, he nearly collapsed with relief.
Then he narrowed his eyes.
Why were you so calm?
How were you not losing your mind over this?
Unless…
Oh, no.
Maybe Black hadn't spoken to you yet. And if you didn’t know yet...
Sebastian’s breath caught.
He was going to have to break this humiliating, horrible, life-ruining news.
And there was no dignified way to do it.
Taking a steadying breath, he strode up to you, his pulse hammering in his throat.
“Hey,” he greeted, voice as casual as he could make it.
You turned to him with an easy smile. “Hey.”
Sebastian stared at you, waiting—praying—for some sign of recognition. Some hint that you already knew what he was about to say.
But you just looked at him expectantly, utterly unaware of the existential crisis unfolding inside him.
His stomach sank.
Oh, fuck. You really don’t know.
Sebastian swallowed, suddenly unsure how to even begin.
“So,” he started, voice tight. “How was your day?”
You blinked at him. “Fine. Yours?”
Sebastian let out a sharp, humorless laugh. “Could’ve been better.”
You hummed, tilting your head at him. “Oh? Something on your mind?”
Sebastian just stared.
Something on his mind? Something on his mind?!
Did you have any idea the kind of mental gymnastics he had been performing all day?
He dragged a hand through his hair, forcing his voice to stay even. “Did… Black speak to you today?”
You blinked, brow furrowing. “The Headmaster?”
“Yes.”
Your frown deepened. “Why would he?”
Sebastian’s pulse spiked.
Oh, fuck. Oh, fuck, oh, fuck, oh, fuck—
“Well.” He exhaled sharply. “I don’t know. But he, uh, might’ve mentioned you.”
You tilted your head, expression unreadable. “Oh? And why would he do that?”
Sebastian felt sick.
“That’s… not important,” he muttered. “Did he seem… suspicious of you?”
You shrugged. “Not that I noticed.”
Sebastian’s stomach was in knots. “Right. Right. That’s good.”
You studied him, your expression flickering just slightly—too observant.
“Why?” you asked, ever so innocent. “Did something happen?”
Sebastian let out a sharp, humorless laugh. “Happen? No, no, nothing happened, just that the bloody Headmaster of Hogwarts apparently thinks we’ve been—”
Your brows lifted, lips twitching in a way that made him deeply uneasy.
“Been…?”
Sebastian groaned, resisting the urge to physically collapse.
“Black thinks we’ve been sneaking off to do improper things,” he muttered, low and fast.
Your lips parted slightly. “What would give you that impression?”
Sebastian scowled. “Oh, I don’t know,” he said flatly. “Maybe the fact that he directly accused me of it. And then had the audacity to start talking about marriage.”
You made a strangled noise.
Sebastian’s eyes narrowed. Had you just laughed?
No. No, surely not—
You cleared your throat. “And what did you say?”
Sebastian let out a sharp breath. “I—I denied it, obviously! But he just kept pushing, talking about consequences and reputation and—”
He was spiraling again. Before he could stop himself, the words tumbled out:
“Look, I swear I would never ruin your future like that—unless you wanted me to, I mean—wait, no, that's not what I meant, just that—”
Sebastian froze. His entire life flashed before his eyes.
Your expression barely wavered. Barely.
But he saw it.
The flicker of amusement. The way your lips twitched. The way you were struggling— visibly struggling—to hold back laughter.
Sebastian’s stomach dropped. His entire body went rigid.
“What?” he demanded.
You shook your head too quickly. “Nothing.”
“No. No, not nothing.” He studied your face closely. “You’re enjoying this!"
You shrugged, playing innocent. “Enjoying what?”
Sebastian groaned, rubbing a hand over his face. “Merlin, I’m going to lose my mind.”
You just patted his shoulder. “Sebastian… we have been sneaking off to do improper things.”
Sebastian swallowed, hard. “Yes, well—” His voice cracked. He cleared his throat violently. “That’s— I mean— Not that I— We weren’t—”
You grinned. “Oh? What was that? We weren’t what?”
Sebastian’s brain short-circuited. His entire spine burned, every memory of exactly what the two of you had been up to flashing through his mind at lightspeed.
The Undercroft. The hidden corridors. The darkened corners of the library. The breathless, desperate whispers beneath the canopy of the Forbidden Forest.
And now Black was onto him.
Sebastian groaned, gripping his hair. “Oh, for Merlin’s sake—this isn’t funny!"
You beamed at him. “It’s a little funny.”
“It’s not.”
“It is.”
Sebastian dropped his hands, exhaling sharply. “I hate you.”
You giggled. Actually giggled. “No, you don’t.”
Sebastian clenched his jaw. He was so close to losing his mind. “I might.”
You patted his cheek. “Keep telling yourself that, darling.”
Sebastian froze. You had never called him that before. His entire body locked up. His thoughts derailed completely.
You, unbothered, turned on your heel and started toward the entrance of the Great Hall.
Sebastian stared after you, unmoving.
It took him a full five seconds to realize he was still standing there, completely useless, thoughts looping in an endless, embarrassing cycle.
And then, as if his day couldn’t get any worse—
A voice drawled behind him.
“Well. That was painful to listen to.”
Sebastian whipped around.
Ominis stood a few feet away, arms crossed, his usual neutral expression tinged with something suspiciously close to amusement.
Sebastian groaned, dragging both hands down his face as he stumbled toward the nearest bench and all but collapsed onto it. He slumped forward, resting his elbows on his knees, staring blankly at the ground as if he could will himself out of existence.
Ominis, still wearing that annoyingly neutral expression, walked over at a much more measured pace and lowered himself onto the bench beside him.
Sebastian exhaled sharply, rubbing his temples. “I don’t get it.”
Ominis hummed, tilting his head slightly. “That’s hardly a surprise.”
Sebastian scowled at him. “I mean her.” He gestured vaguely toward the exit, where you had disappeared moments ago, completely unbothered by what should have been a catastrophic situation.
“She’s amused,” Sebastian muttered, half to himself. “She’s enjoying this. Why?”
Ominis considered for a moment, then exhaled through his nose. “Well,” he said, his voice slow, patient—annoyingly reasonable—“to be fair, you did a terrible job explaining why this is an actual problem.”
Sebastian blinked at him. “Excuse me?”
Ominis turned his head toward him, a single brow arching. “Think about it. You just ambushed her out of nowhere, looking like a deranged madman, started rambling about Black and improper behavior, and then, instead of clearly conveying the very real threat to your future, you panicked so hard that you practically proposed to her.”
Sebastian groaned again, louder this time. “That is not what happened.”
Ominis smirked slightly. “That is exactly what happened.”
Sebastian waved a hand, desperate to move past that particular humiliation. “Fine, whatever. But she should still be worried. Black is onto us. He’s already talking about arranged marriages—”
“Is he?” Ominis interrupted, ever-so-slightly skeptical.
Sebastian gawked at him. “You were there! You heard him!”
Ominis inclined his head slightly. “I was there, yes. But let’s be rational about this, Sebastian.”
Sebastian scoffed. “Oh, great, here comes the ‘rational’ lecture.”
“You and her have been sneaking off together, and to the best of your knowledge, no one has caught you. And then, suddenly, Black of all people, corners you, accuses you, and starts spewing about ‘respectable arrangements’ without a shred of actual proof."
Sebastian frowned. “What's your point?"
Ominis tilted his head slightly, replaying the conversation in his mind. “I mean that Phineas Nigellus Black has never once given a single damn about student affairs. Not once in the years we’ve been here. He barely even tolerates his job as it is. And yet today he suddenly decides to take a keen interest in your extracurricular activities? And not just an interest, but one so pressing that he practically corners you in broad daylight and starts talking about marriage?”
Sebastian frowned deeper, his hands resting on his knees. He hated to admit it, but… Ominis had a point.
“That does seem… uncharacteristically involved of him,” Sebastian admitted, chewing his lip.
Ominis nodded once. “Exactly. It’s suspicious.”
Sebastian shook his head, running a frustrated hand through his hair. “Alright, fine. But maybe—maybe, I don't know, maybe Garreth ran his mouth in the vicinity of a Professor and it got back to Black?”
Ominis considered this for a moment, then shook his head. “If that were the case, it still wouldn’t explain his reaction. He’d have let that Professor handle it, or sent you a warning through a letter—he wouldn’t waste time personally terrorizing you.”
Sebastian exhaled sharply. “So what are you saying, then?”
Ominis’ brows furrowed slightly. “I’m saying something about this doesn’t make sense.
Sebastian frowned. “Maybe not, but he is an odd man. Who knows what goes on in his head.”
Ominis was silent for a long moment, then—slowly, so slowly—his lips curved into something dangerously close to amusement.
“Oh, this is good,” he murmured, tilting his head as though savoring the realization.
Sebastian snapped his head toward him. “Excuse me?”
Ominis let out a short breath—not quite a laugh, but something suspiciously close. “Oh, come now, Sebastian. Think about it. There’s no way it was actually Black. He knew far too much about the specific details of your late night rendezvous. The only logical conclusion is that someone must have impersonated Black. Someone who knows you. Obviously one of our friends went through the absolute ordeal of brewing a Polyjuice Potion just to terrorize you.”
Sebastian’s eyes narrowed. “He did know a lot about where precisely we’ve snuck off to… the library, hidden alcoves...”
“Exactly,” Ominis said, clearly entertained.
Sebastian growled in frustration, pushing off the bench to stand. His blood was boiling. Ominis was right.
The fucking audacity.
His mind raced, already running through the short list of people who were both deranged enough and competent enough to pull this off.
And one name immediately shot to the top of his list.
“Garreth.”
Ominis, still looking entirely too pleased, lifted a brow. “Hmm?”
“It’s got to be Garreth.”
Ominis exhaled, leaning back slightly against the bench. “And what, exactly, makes you so certain?”
Sebastian threw out a hand. “Are you kidding? He’s been up my arse all week, badgering me for details about—” He cut himself off.
Ominis smirked. “About?”
Sebastian gritted his teeth. “About… things.”
Ominis’ smirk deepened. “Oh, I’m well aware of your things, Sebastian.”
Sebastian groaned. “Shut up.”
Ominis hummed, utterly unbothered.
Sebastian paced in front of him, hands in his hair, his entire body tense with fury.
“I’ve been telling him way too much,” Sebastian muttered, seething. “I knew I shouldn’t have let my guard down. But he kept asking, and I figured, what’s the harm? It’s not like he’d—”
He stopped short, realization hitting him like a brick.
“…Wait.” Sebastian’s eyes widened. “That absolute MENACE.”
Ominis lifted a brow. “What?”
Sebastian turned back to him, looking truly unhinged now. “He’s been gloating about a new potion all week.”
Ominis’ smirk vanished.
Sebastian pointed at him, vicious with victory. “He said—and I quote—‘Oh, it’s a special project. I’ll tell you about it when the time is right.’”
Ominis actually winced. “Oh.”
“Oh?” Sebastian mimicked, mocking. “Oh? Yeah, Ominis, oh. The bastard’s been cooking up a Polyjuice Potion for weeks, and I didn’t even see it. I played right into his hands. Merlin’s beard.”
Ominis considered this for a moment. Then: “That’s… actually quite impressive.”
Sebastian nearly exploded.
“DON’T ENCOURAGE HIM!”
Ominis snorted. “Oh, come on. You have to admit—it’s kind of brilliant.”
Sebastian whirled back around, pacing furiously. “I’m going to kill him.”
Ominis chuckled.
“No, I’m serious,” Sebastian hissed. “I am going to personally, violently, and enthusiastically end Garreth Weasley’s entire bloodline.”
Ominis shook his head, but he was clearly entertained.
Sebastian’s mind was already racing with vengeance. Garreth wanted to play games? Fine. Sebastian would play. And Garreth Weasley was about to regret every single life choice that had led him to this moment.
Headmaster Phineas Nigellus Black had many regrets in life.
Taking the position as Headmaster of this cursed institution was certainly among them.
There were only so many years a man could tolerate insufferable teenagers, incompetent professors, and Ministry interference before he began to wonder whether he had been cursed by some malevolent higher power.
And now—now—on top of it all, he had to deal with this.
He had been enduring—not enjoying, enduring—his evening tea in his office when Professor Sharp casually mentioned something that instantly ruined his entire day.
“So. About this marriage arrangement of yours.”
Black had, understandably, nearly choked to death on his own tea.
Sharp, ever unbothered, merely watched him struggle, raising a single brow in mild disinterest.
Black coughed violently, pounding a fist against his chest, before spluttering, “My WHAT?”
Sharp had the audacity to look unimpressed.
“I assumed it was a joke,” he said, calm as ever. “But it’s already making the rounds among the students, so I thought I’d ask before it reaches the parents.”
Black stared at him. It took an impressive amount of effort for him not to throw something.
“…Please explain,” he said through gritted teeth.
Sharp tilted his head. “There’s a rumor circulating that you threatened Sebastian Sallow with an arranged marriage.”
Black froze. The words did not compute.
“What.”
Sharp, utterly unconcerned, took a sip of his tea. “Something about improper behavior, a scandal, and the need for a ‘respectable arrangement.’”
Black’s eye twitched.
“Why,” he began, voice tight, “would I ever, in any universe, concern myself with the sordid affairs of adolescent imbeciles?”
Sharp exhaled, as if he, too, was burdened by the weight of other people’s idiocy.
“That,” he said, setting his tea down, “is an excellent question.”
Black rubbed his temples. He had much better things to do than play wedding officiant to a bunch of lovesick idiots. Which meant someone—some absolute fool—had used his name in vain.
And Black was going to find out who.
“Summon Weasley,” he snapped.
Sharp inclined his head. “Garreth or Matilda?”
Black paused. Then, slowly, a deep sense of dread filled him.
“…Both,” he muttered.
And thus, his investigation began.
Garreth Weasley was about to have a very bad day.
He just didn’t know it yet.
Currently, he was completely at ease, perched on the edge of a courtyard fountain, chatting animatedly with a group of Hufflepuffs. His hands were moving wildly, eyes bright with mischief, completely unaware that his life expectancy had just significantly shortened.
Because Sebastian Sallow was on the warpath.
With Ominis reluctantly trailing behind him, Sebastian marched across the courtyard, his eyes locked onto his target like a predator about to tear its prey to shreds.
“Garreth Weasley!”
The Hufflepuffs startled.
Garreth turned his head, blinking in surprise as Sebastian stormed toward him, seething with righteous fury.
“Ah, Sebastian,” Garreth greeted, flashing his usual easy grin. “To what do I owe the pleasure?”
Sebastian didn’t stop until he was right in front of him, glaring so hard it was a miracle Garreth’s hair didn’t catch fire on the spot.
“You know damn well why,” Sebastian growled.
Garreth blinked. “...I don’t, actually.”
Sebastian leaned in, voice low and dangerous. “Drop the act, Weasley. We know.”
Garreth, to his credit, didn’t falter.
“Know what, exactly?” he asked, tilting his head.
Sebastian scoffed. “Oh, don’t play dumb. You used a Polyjuice Potion to impersonate Black and humiliate me,” he snapped. “Admit it.”
Garreth’s brows lifted. “I did what?”
Sebastian narrowed his eyes. “Oh, don’t.”
“I’m serious,” Garreth said, now actually looking intrigued. “Someone turned into Black? That’s brilliant.”
Sebastian made a noise that was not human.
Ominis sighed. “Garreth, please. Just confess so Sebastian doesn’t do something regrettable.”
Garreth scoffed. “You think I’d waste a whole month on a potion just to mess with Sallow?”
Sebastian’s eye twitched.
“YES.”
Garreth paused. “…Okay, fair. But I didn’t.”
Sebastian stabbed a finger into his chest. “You’ve been asking questions, Weasley. About—about my, my nightly... routine. And— and gloating about a special potion.”
Garreth looked entirely too delighted. “Wait, someone impersonated Black and then they interrogated you about your sex life?”
Sebastian’s rage doubled. “I’m going to strangle you.”
Ominis rubbed his temples. “Sebastian, perhaps—”
“NO.” Sebastian cut him off, eyes still locked on Garreth. “I am not leaving until this idiot admits—”
“Mr. Sallow.”
A new voice. One that sent an icy chill down all their spines.
Sebastian turned slowly.
There, standing just a few feet away, expression unreadable, was Professor Sharp, and beside him, arms crossed, lips pressed into a thin line, was Professor Weasley.
Then, after a long pause, Sharp spoke.
“Well,” he said dryly, eyes flicking between them. “It seems you’ve come to the same conclusion as the Headmaster regarding who exactly impersonated him this morning.”
Sebastian froze.
Sharp’s gaze shifted.
To Garreth.
The Gryffindor, who had been watching the exchange with mild amusement, suddenly looked deeply alarmed.
“What?” he said, blinking rapidly. “No, no, no. I didn’t—”
Professor Weasley let out a heavy sigh. “Garreth.”
Garreth turned to her, eyes wide with betrayal. “Aunt Matilda, I swear, I did not—”
“We’ll discuss it in the Headmaster’s office,” she said firmly.
Garreth’s jaw dropped. “Are you serious?! I had nothing to do with this!”
Professor Weasley exhaled, rubbing her temples. “Garreth, it’s always you.”
Garreth threw out his arms. “That’s unfair!”
Sharp arched a brow. “Is it?”
Garreth opened his mouth, paused, then scowled.
“…A little,” he muttered.
Professor Weasley stepped forward, placing a firm hand on Garreth’s shoulder.
“Come along,” she said, her voice leaving no room for argument.
Garreth whirled on Sebastian. “I hope you’re happy, Sallow!”
Sebastian blinked. Was he happy? Garreth was being dragged away, right in front of him. He should have felt vindicated. Should have felt relief.
Instead—
There was a deep, sinking dread curling in his stomach.
Because Garreth’s arrest was not the problem. The problem was the real Headmaster now knew about all of this.
And Sebastian was still very, very screwed.
As Garreth was pulled away, still pleading his case, Sebastian stood there, motionless, watching his chance at containment disappear before his eyes.
Ominis let out a slow breath.
“Well,” he murmured. “That didn’t help at all, did it?”
Sebastian’s stomach churned.
“…No.”
No, it did not.
And little did Sebastian and Ominis know, you had been listening the entire time.
And it was glorious.
You had been casually passing through the courtyard—entirely innocent, of course—when you had spotted Sebastian storming toward Garreth like a vengeful wraith.
Naturally, you had done the only reasonable thing and tucked yourself behind a nearby pillar to observe.
And Merlin’s beard, was it worth it.
Sebastian, red-faced and seething, had all but shoved his accusations down Garreth’s throat.
Garreth had been just as bewildered as expected.
And Ominis? Ominis had just stood there, his entire existence radiating exasperation.
You’d had to bite your knuckles to keep from laughing.
Then came the real highlight—Professor Sharp and Weasley arriving just in time to drag Garreth away.
And Sebastian? He wasn’t relieved.
Oh, no.
If anything, he looked even more panicked, and you had to physically restrain yourself from cackling out loud.
As the crowd dispersed and Sebastian muttered something about heading to the Undercroft, your mind was already racing.
You had one last dose of Polyjuice Potion.
And you were going to use it well.
Sebastian and Ominis walked briskly through the halls, heading toward the passage that would take them to the Undercroft.
Sebastian was still fuming.
“I can’t believe this,” he muttered under his breath. "What if the real Black actually agrees with Garreth’s idiotic ramblings and—"
Ominis exhaled sharply. “Sebastian, I highly doubt the Headmaster is actually considering an arranged marriage for you.”
Sebastian threw out his hands. “Are you sure? Because I’M NOT.”
Ominis pinched the bridge of his nose. “For the last time, Black does not care.”
“You don’t know that,” Sebastian shot back. “What if he decides to make an example of me? What if this turns into some grand moral statement about propriety?”
Ominis snorted. “Phineas Nigellus Black making a moral statement? That would imply he had morals to begin with.”
Sebastian hesitated. “…Okay, fair. But still—”
A voice cut through the corridor.
“Mr. Sallow.”
Sebastian stopped dead.
Ominis visibly tensed.
Both of them turned.
There, standing at the end of the corridor, arms folded behind his back, expression severe, was Headmaster Black.
Or at least, who they assumed was Black.
Sebastian felt every last ounce of his blood drain from his face as the Headmaster took slow, deliberate steps toward them, gaze piercing.
“I have been informed,” he said, voice low and authoritative, “that you took justice into your own hands this afternoon.”
Sebastian’s stomach plummeted.
Ominis stood unnaturally still, as if movement might invite further scrutiny.
“That is—” Sebastian stammered, “I was just—”
Black lifted a hand.
Sebastian shut up.
“As I was saying,” the Headmaster continued, voice measured, “It is not your place, Mr. Sallow, to interrogate your peers. Confronting Mr. Weasley? Threatening him in front of witnesses?”
Sebastian’s blood ran cold.
“That’s not—I didn’t threaten him, I just—”
Black tilted his chin downward.
Sebastian closed his mouth.
“Since you are so concerned with matters of conduct and discretion,” Black continued, “I think it only fitting that you learn about them properly.”
Sebastian blinked.
“Sir?”
“You will come with me to Professor Ronen’s office,” Black declared, “where you will complete a ten-foot essay on—”
Sebastian braced himself.
“—Why One Must Be Discreet in Matters of the Heart.”
Sebastian stared.
Ominis made an awful noise, half-choking, half-suppressing a laugh.
Sebastian’s brain shut down.
“What.”
Black did not waver.
“You heard me, Mr. Sallow.”
Sebastian gawked at him. “You—you cannot be serious.”
“I am always serious.” Black’s voice brooked no argument.
Sebastian sputtered. “Sir, this is completely unnecessary—”
“Oh?” Black arched a brow. “Would you rather I speak with Professor Weasley about additional disciplinary measures?”
Sebastian shut his mouth.
Black smirked.
“Good,” he said crisply. “Now, off we go.”
Sebastian gritted his teeth, threw one last murderous look over his shoulder at a still-chuckling Ominis, and stalked off after Professor Black, who continued his merciless monologue.
“…lack of discretion, lack of foresight, lack of even the most basic self-preservation instincts,” Black droned, his tone a perfect balance of condescension and boredom.
Sebastian gritted his teeth. “Yes, sir.”
Black didn’t even acknowledge the response. “One might assume, given your track record, that you would at least attempt to be subtle in your misdeeds.”
Sebastian barely resisted the urge to fling himself out of the nearest window.
“Yes, sir.”
Black sighed. “And yet, instead of exercising the tiniest sliver of caution, you took it upon yourself to corner a fellow student and create a spectacle of your impropriety.”
Sebastian’s eye twitched.
“Yes, sir.”
Black hummed, as though unimpressed. “Honestly, Sallow, I don’t know whether to be more appalled by your recklessness or by your utter incompetence in getting away with it.”
“Yes. Sir.”
By the time they reached Professor Ronen’s office, Sebastian was seething.
Black didn’t even bother knocking. He simply swept inside, looking entirely too pleased with himself, and gestured for Sebastian to enter.
Sebastian dragged his feet as he stepped inside, his mood absolutely foul.
Professor Abraham Ronen looked up from his desk, his ever-cheerful expression brightening further as he spotted them.
“Ah, Headmaster!” he greeted, standing swiftly. “And Mr. Sallow. To what do I owe this unexpected visit?”
“I require your assistance, Professor Ronen,” Black said smoothly, stepping into the room with the air of a man who had never known shame in his life. “Mr. Sallow has demonstrated a profound inability to conduct himself with even the faintest whisper of discretion.”
Sebastian wanted to melt into the floor.
Ronen’s brows lifted slightly. “Discretion, sir?”
Black sighed dramatically, as if personally burdened by Sebastian’s existence.
“Yes,” he said. “You see, I have taken it upon myself to educate young Sallow in the ways of proper decorum.”
Sebastian scowled. “That is not what happened.”
Black lifted a hand. “Did I give you permission to speak?”
Sebastian’s fury burned hotter. “No, but—”
“Then don’t.”
Sebastian bit his tongue so hard he nearly drew blood.
Ronen tilted his head, clearly amused. “And what exactly does this… education entail, Headmaster?”
“I am assigning Mr. Sallow a ten-foot essay,” Black said blandly, as if discussing the weather, “on Why One Must Be Discreet in Matters of the Heart.”
Ronen blinked.
Sebastian wanted to die.
“I would like you to supervise, Professor,” Black continued smoothly, “to ensure that Mr. Sallow completes his work with the appropriate level of… humility.”
Sebastian felt himself short-circuit.
Ronen was trying very, very hard not to laugh. “Oh, I would be honored.”
Sebastian whirled on Black, aghast. “Sir, please—”
Black lifted a hand.
Sebastian shut his mouth.
Black smirked.
“Good. Now, I expect this to be completed by this evening. Professor Ronen will be responsible for ensuring its quality, and I will personally review it myself.”
Sebastian groaned audibly.
Black tilted his head. “Was that a complaint, Mr. Sallow?”
Sebastian gritted his teeth. “No, sir.”
“Excellent.”
Black turned on his heel, his robes sweeping dramatically behind him as he made his exit.
As soon as the door clicked shut, Ronen let out a deep, satisfied sigh.
“Well,” he said cheerfully. “This is easily the highlight of my week.”
Sebastian glared daggers at him.
Ronen just chuckled.
“Now, now, Mr. Sallow,” he said, far too pleased with himself. “Take a seat.”
Sebastian huffed angrily and collapsed into the chair, arms crossed like a petulant child.
Ronen leaned against his desk, grinning. “So,” he mused. “Matters of the heart, hmm?”
Sebastian had never felt more humiliated in his life.
Which was saying something, considering he’d spent the entire day careening from one public disaster to another.
Late that night, you sat cross-legged on one of the worn couches in the Undercroft, a book balanced on your lap, pretending to be deeply engrossed in whatever passage your eyes were lazily skimming. Across from you, Ominis sat in his usual chair, his own book in hand, posture relaxed.
The two of you had settled into companionable silence, save for the occasional turn of a page and the steady sound of the flickering torches along the stone walls.
He had, of course, informed you—thinking you had no idea—that Sebastian had been assigned detention.
Though he had spared the details, he had smirked slightly as he’d said, “I’m sure we’ll both get an earful about it later.”
And oh, how right he was.
Sebastian was going to be livid. And you were going to have to try very, very hard to look appropriately concerned.
The entrance finally creaked open.
A familiar set of footsteps echoed through the stone chamber.
You looked up and nearly lost it.
Sebastian stood in the archway, fuming. His hair was a mess. His robes were askew. And his hands—oh, his hands—
You had expected anger. You had not expected him to look like he had crawled out of an ink well after fighting for his life.
Ominis, still not looking up from his book, greeted him far too calmly. “Sebastian.”
“I,” he seethed, glaring at nothing in particular, “am going to kill Phineas Nigellus Black.”
Ominis exhaled heavily, not even looking up from his book. “That seems excessive.”
Sebastian ignored him. He threw himself onto the couch beside you, huffing furiously. You had never seen him so pissed off. It was glorious.
You bit the inside of your cheek to keep from laughing.
Instead, you blinked at him, feigning concern.
“Rough night?”
Sebastian turned his scathing glare on you.
Oh, it took everything in you not to crack.
“I had to write,” he growled, slamming a fist onto the armrest, “a TEN-FOOT ESSAY.”
You blinked innocently. “Oh?”
Sebastian threw up his hands. Ink smudged across his face.
“It was absolute TORTURE,” he ranted, pacing now, gesturing wildly. “Ronen wouldn’t let me leave until he was satisfied with it—AND I HAD TO READ IT ALOUD.”
Ominis inhaled sharply. Your lips twitched.
Then.
Ominis broke. The laugh that tore out of him was far louder than you had expected, his usually composed demeanor utterly shattering.
And now, with Sebastian’s utter misery in front of you, with Ominis losing his composure entirely, you couldn’t stop the wheeze that escaped, followed by absolute uncontrolled laughter.
It burst out of you before you could stop it, filling the Undercroft, your entire body shaking with mirth.
Sebastian whipped around, eyes wild with betrayal.
“YOU’RE LAUGHING?!”
You tried—oh, you tried—to compose yourself. But every time you thought you had it under control, you caught sight of Sebastian’s ink-stained hands, his utterly ruined dignity, the absolute rage burning in his eyes—
And you lost it all over again.
Ominis, already a goner, was curled forward, clutching his stomach, his laughter echoing off the stone walls.
Sebastian scowled so hard it could have cracked the very foundation of Hogwarts.
“You think this is FUNNY?” he barked, crossing his arms.
You gasped for breath, wiping at your eyes. “No—no, of course not.”
Sebastian glared. “Liar.”
You bit your lip, still grinning. “It’s just… I’m so sorry, Sebastian,” you said, completely unconvincing.
He jabbed a finger at you. “No, you’re not.”
You shrugged, trying—and failing—to keep a straight face. “Maybe a little.”
Sebastian groaned, dragging both hands down his face.
"It's—it's just—imagining your reading it aloud," you inhaled sharply as if you were dying for oxygen, "Matters of the Heart—"
You dissolved into laughter again, but Sebastian froze.
Stared.
Blinked.
Looked at his hands.
Then looked at you.
Then back at his hands.
Realization dawned on you. The laughter immediately died in your throat.
Fuck.
"I didn't tell you what the essay was about," Sebastian said slowly,
Your brain short-circuited.
Lie. Lie, quickly.
“Oh—uh—” You scrambled for an excuse. “I mean, it was—it was obvious, wasn’t it? What else would Black make you write about?”
Sebastian’s eyes darkened.
Ominis exhaled sharply. “Oh,” he murmured, realization dawning.
You clenched your fists. Shit.
Sebastian leaned in slightly, his voice dropping into something smooth, silky, utterly lethal.
“You knew.”
It wasn’t a question. It was a statement. A verdict. A sentence.
You forced out an awkward chuckle. “Sebastian, come on—”
“You knew,” he repeated, glaring. "How did you know?"
Ominis made a noise of delighted horror. “Oh, this is about to be so good.”
You swallowed hard.
Sebastian was too sharp. Too quick. He was already piecing it together—his expression shifting from betrayal to slow, creeping realization.
“How did you know?” he demanded.
You sunk back into the cushions, hands raised in a feeble attempt at innocence.
“Sebastian—”
His brow furrowed. His eyes narrowed. And then, softly, dangerously—
“…It was you.”
Your breath caught.
Sebastian stilled.
Ominis gasped.
And then—
“IT WAS YOU!”
He knew.
Oh. Oh, fuck.
Your body tensed, preparing to run.
Sebastian saw it.
"YOU LITTLE MENACE!"
You yelped, narrowly missing his outstretched hand as you flew over the sofa.
“SEBASTIAN—WAIT—”
“NO.” He vaulted over the couch in pursuit. “YOU’RE DEAD.”
You sprinted, dodging past Ominis's chair, laughing too hard to breathe.
“You absolute menace!” Sebastian shouted, nearly grabbing your wrist. “YOU MADE ME THINK I WAS GETTING MARRIED.”
You shrieked with laughter. “It was a joke—”
“A JOKE?!”
You ducked behind a column, barely missing Sebastian’s grasp.
“Sebastian, listen—”
“NO.” He vaulted over the sofa, closing the gap. “I AM GOING TO KILL YOU.”
“I CAN EXPLAIN—”
“OH, YOU’D BETTER.”
“IT WAS A PRANK—”
Ominis, now fully invested, wiped tears from his eyes. “I have never been happier.”
Sebastian rounded the pillar. You darted left. He anticipated it. He grabbed at your wrist—
And this time, he caught you.
Momentum dragged both of you down, and you landed hard on the floor, pinned beneath him.
Your chest heaved from laughing too hard.
Sebastian, equally breathless, stared down at you.
For a moment, neither of you moved.
The Undercroft was too quiet now.
You felt the weight of him, the warmth of his hands wrapped around your wrists, pressing into the floor on either side of you.
“…You’re in so much trouble,” he muttered, but his voice had dropping lower, rougher.
Your breath hitched. You weren’t laughing anymore.
Ominis, who had been utterly entertained up until now, cleared his throat loudly.
“Right,” he said flatly, dragging his hand down his face before heading to the door. “This is officially no longer my business.”
Neither of you moved. Neither of you breathed.
Sebastian’s fingers tightened.
Oh.
Oh, you were so screwed.