Pairing: Sebastian Sallow x Reader
Summary: You stayed up too late replaying Hogwarts Legacy. Just one more run. One more goodbye to the boy with too much to handle and no one left in his corner. You hit 100% completion.
Everything done. Everything perfect.
And then you fell asleep.
But you wake up in the Undercroft.
Sebastian Sallow-real, alive, and seconds from hexing you-is standing over you with his wand drawn. The story hasn't ended. It's still happening. But now, you're inside it. No wand. No plan. No way back. And nothing to explain your existence.
Content & Trigger Warnings (18+): Explicit sexual content (NSFW), raw intimacy, oral (f. receiving), penetrative sex, light pain kink, overstimulation, time-slip/self-insert themes, consent emphasized but emotionally charged.
A/N: This is a standalone one-shot. Emotional development would unfold more gradually in a full-length fic.
This is part of a fanfiction concept that may eventually become a full-length book-but for now, I just wanted to explore it as a single, self-contained scene.
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You set the controller down and sigh. The cutscene plays out—same as always. You’ve seen it five times now. OWLs complete. House Cup secured. This time, you even hit 100%. Every side quest, every hidden chest, every Merlin Trial. It’s all finished. Finally.
And still, something’s missing.
He should be here. He deserves to be standing with everyone else, part of the celebration. But for whatever reason, he never is. You never sent him to Azkaban—you couldn’t. No matter how many times you replay the game, you always choose to let him go.
The credits begin to roll, and your eyes are already heavy. It’s late—past 3 a.m.—and you’ve been playing for hours. The soft music wraps around you, familiar and final. You sink back into your blankets, eyes slipping shut, heartbeat slowing.
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Your head feels heavy, like you’ve been asleep for years. For a second, you assume you’re still in bed—maybe you passed out with the TV on again. But you smell something different, something heavy: dust. Musty air. A weird hum beneath it all.
You’re lying on stone flooring, the surface cool beneath your bare thighs. Torch light flickers across the walls. Boxes are scattered around the room. You recognize the architecture immediately—the Undercroft. From the game.
What the hell kind of dream is this?
You slowly sit up and glance down at yourself. You’re still in the clothes you fell asleep in: your oversized frog-print T-shirt and a pair of black underwear. Your cow slippers—lopsided and slightly scuffed—are still somehow on your feet. The sight of them against the stone is so ridiculous it almost makes you laugh.
Your stomach drops as you recognize the voice.
He stands just ahead, half-obscured by the shadows curling around the Undercroft’s columns. His wand is raised—aimed directly at you—and there’s no trace of the familiar smirk you’ve seen a hundred times in cutscenes. He’s taller in person. Broader. Tousled brown hair falls just above his brow. His robes hang open, his vest wrinkled, tie loose, and collar undone like he dressed in a hurry.
His face is freckled—faint, scattered across his nose and cheekbones, especially vivid in the flickering light. And his brown eyes pin you in place with suspicion.
He looks real. He feels real.
And he is seconds away from hexing you.
“That’s… quite the outfit to wear sneaking into a place like this.”
You follow his stare and freeze.
He looks completely floored. Not just confused—stunned. Like he’s never seen so much bare leg in his life and can’t decide if you’re cursed or criminal.
But the cold is real. The silence is too loud. The feeling of his gaze on your skin makes you hyper-aware of every breath you take. And the way he’s watching you feels far too precise to be imagined.
You scramble to your feet and throw your hands up in surrender.
“I—I don’t know how I got here,” you say quickly. “My name is Y/N. I woke up here!”
“How did you find this place?”
“I told you—I don’t know!”
“Liar,” his voice snaps. “Try again.”
“I was in my room!” you blurt. “It was late. I fell asleep and then—I woke up here. I was playing a game!”
“A game?” His eyes narrow. There’s a flicker of disbelief. The wand stays up. “You expect me to believe that?”
“Not really,” you say, lifting your hands higher. “But it was worth a shot.”
You shift your weight, and glance around the room—searching for something to anchor you. “I really can’t tell if I’m dreaming or not.”
Sebastian moves suddenly—just one quick step forward, wand lifting higher, and the movement is so real, so close, that you flinch.
“Sebastian!” The name leaves your mouth instinctively.
“Yes,” you breathe. “I know you because of the game. I know this place is called the Undercroft. I know your best friend—Ominis Gaunt—was the one who found it first.”
He doesn’t move, but something shifts in his expression. Something unsettled.
“Impossible,” he says tightly. “Tell me who you are.”
“Look,” you say quietly. “I’m from the year 2025. This place—Hogwarts, this world—it’s not supposed to be real where I’m from. It’s fictional. It’s… a story.”
He stares at you like you’ve gone mad.
“It’s a game,” you continue. “You’re in it. I played it. I watched your story unfold through a character with ancient magic.”
“Explain,” he says, voice barely audible. But the wand stays up. The tension doesn’t leave the room.
You tell him about screens, about controllers, about pixels and code and decision-based dialogue trees. You try to explain what a video game is, what Hogwarts Legacy is, how you explored every part of this world—from the Highlands to Hogsmeade—and how he was always your favorite part of it.
The whole time, he says nothing.
But his grip on the wand loosens. Just a little.
“Ancient magic…” he hums after you finish explaining. His tone is thoughtful, but there’s something brittle under it. “You’re talking about Milton Shagworthy.”
“Milton Shagworthy,” he repeats, completely serious. “He’s the new fifth-year. Helped me with the Scriptorium. With Anne. All of it.”
You choke on a laugh. “Milton Shagworthy? Who—who named their character that?”
He shrugs, unfazed. “I don’t know. But that’s who you just described.”
You’re still laughing. “You’re telling me someone made a custom character, named him Milton Shagworthy, and played through your life like it’s a joke—and you’re just fine with that?”
He raises a brow. “I’m not fine with it, I’m just telling you what’s real. Apparently.”
“And I’m telling you… it was a game. You were in it. That story? It’s something we play. Make choices in. Milton Shagworthy is the result of someone’s really unfortunate imagination.”
He’s quiet for a long time.
“Then you know what I did.”
He doesn’t look at you, but you see it—how his shoulders tighten, how his grip on the wand slackens just slightly. Like something cracked open inside him and hasn’t been sealed since.
“I’m sorry,” you murmur. “I didn’t mean—”
It’s not harsh. Just… hollow.
You hesitate, then take a cautious step forward.
That gets a reaction. He lets out a short, bitter laugh. “Help me? How could you help me?”
You meet his gaze and hold it.
“Because I’ve seen what comes next. In the game, your story ends—or fades into the background—but here? It’s still happening. You’re still in it. And maybe that means I’m not just here by accident. Maybe I’m here to help you get through it.”
He doesn’t respond. Just watches you for a moment—long enough to make your heart stutter. His wand lowers an inch, then two, until it’s finally at his side.
That alone feels like a truce.
He sighs, like he’s weighing his options. Then, without a word, he steps back and gestures—barely—with a tilt of his head.
You settle onto one of the wooden boxes, the edge creaking softly beneath you. He doesn’t sit, but he doesn’t stop you either. You’re not close, but you’re not far anymore.
“So,” he says, finally breaking the silence. “You said you were playing the game before you ended up here?”
“And it just… ends like that? My story never finishes?”
You hesitate, then shrug. “Not really. You just kind of disappear. It’s vague. Unresolved.”
He frowns. “That’s absurd.”
“Yeah. A lot of people think so. Which is why they write about what they think happens after.”
“Write?” His brow furrows. “Stories?”
“They call it fan fiction.”
He repeats the words slowly, like he’s tasting them. “And what—these stories… are they good? Do they give me better endings?”
You smile faintly. “Most of them do. Some don’t. Some are completely unhinged.”
You clear your throat. “Some people write… other things.”
His eyes narrow slightly. “Other things?”
“Intimate,” he echoes, cautious.
“They write about you. About you doing… things.”
You hesitate. “Usually themselves. Or their own characters.”
He looks at you. Really looks. “And have you…?”
You raise a hand quickly. “I plead the fifth.”
He watches you for a long moment after that—like he’s still trying to figure you out, still deciding whether you’re real or just a cruel trick played by magic and grief.
You don’t say anything else. Neither does he.
But the silence that follows isn’t as tense as before. It settles between you, strange but not unwelcome.
Eventually, he sits beside you.
Not close at first. But then his shoulder brushes yours as he shifts, and when your thighs touch—briefly—he doesn’t move away.
He glances at you sideways, guarded. Searching.
“You really don’t belong here.”
“I know,” you say with a small shrug. “But I’m here.”
“You’d really help me?” He asks, voice barely above a whisper.
You meet his eyes without flinching. “Without a doubt.”
He looks away fast, jaw tight. “Don’t look at me like that.”
“You couldn’t possibly—” His voice catches. “You couldn’t understand what it was like for me.”
You hold his gaze as the words spill from you.
“Sebastian, I watched you suffer. Alone. I saw the pain. The desperation. The way you love your sister so fiercely it tore pieces out of you. I know.”
He’s breathing hard now. Not from anger. From something else.
“You never deserved to be alone,” you say gently. “And you’re not a monster. Not the one you think you are. You’re not.”
“How could you be a monster for trying to save the people you love?”
Then he moves so fast you don’t even register that his lips are on yours until you’re already kissing him back.
The kiss starts like a detonation—hot, fast, fueled by everything neither of you have said.
Less rushed. Slower. Less like a spark and more like collapse. Like he’s been holding back for so long that now, with your mouth on his, he’s finally unraveling. His hand curls behind your neck, anchoring you in place. The other slips to your thigh, then higher. His palm burns through the fabric of your shirt like it’s nothing.
You breathe against his lips, voice trembling. “Sebastian—”
He doesn’t pull back. Just leans his forehead to yours, panting, brows furrowed like he’s trying not to fall apart.
“You say my name like it means something.”
“This doesn’t make sense,” he says, voice cracking. “You. Here. Wanting me like this.”
“None of it makes any sense,” you say. “But it’s happening.”
You’re still sitting on the wooden crate, knees touching, breath tangled. Your shirt’s falling off one shoulder. His tie is hanging even looser and useless around his neck.
His gaze drops to your lips. “Tell me to stop.”
“I don’t want you to stop,” you say, breathless. “But… I’ve never done this before.”
You can almost hear the gears grinding behind his eyes. “Never?”
His eyes flash—not with lust, but with concern. “And you want this to be with me?”
“I already chose you,” you say. “Every time I played. Every time I watched the story—I chose you.”
He stares at you like you’ve cracked him wide open.
Then he kisses you again. Harder.
And that’s when you feel it—his restraint breaking. His tongue slides along yours, and his fingers tighten on your thigh. He groans into your mouth when you whimper, when you dig your nails into his shirt.
He yanks his vest down his arms, then shrugs out of the shirt underneath, breath shaking. You run your hands over his firm, freckled chest. His body is hot beneath your palms, and you want more.
He pulls your shirt up—pauses just beneath your chest. “Can I see you?”
You nod, and raise your arms.
Your breasts rise and fall with your breath. He’s looking at you like you’re something special—like if he blinks, he’ll miss it.
“Bloody hell,” he breathes. “You’re unreal.”
Your mouth tilts. “You can touch.”
One hand, gentle but desperate, cups your breast. His thumb brushes your nipple until it stiffens under his touch. You moan, and that’s all it takes—his mouth is on your throat, then your collarbone, then down to your chest. His tongue flicks over your nipple. He sucks, just once, and you move into him.
“I want you on your back,” he growls.
He stands, grabs you by the hips, and lifts you off the crate like you weigh nothing. The stone floor is cold against your back, but the heat from his body makes up for it. He kneels between your legs, eyes drinking you in.
You reach for his belt. “Take this off.”
He unbuckles it fast, shoving his trousers down to his thighs. His cock presses against the fabric of his boxers—thick, long, hard, and already leaking.
But he doesn’t touch himself. He’s focused entirely on you.
He crouches over you, fingers slipping under the waistband of your underwear. “These too?”
He pulls them down slowly. The air hits your soaked core and your thighs twitch.
He spreads your legs and settles between them. His hands slide up your thighs, gripping and massaging like he can’t believe you’re real.
You prop yourself up on your elbows just in time to watch his head lower.
Then his mouth is on you.
His tongue licks a long, slow stripe through your folds. Then another. His mouth wraps around your clit and sucks, gentle at first, then firmer, and your hips buck.
He grabs them. “Stay still.”
“Can’t,” you gasp. “I—Sebastian—”
And the sight knocks the breath from your lungs.
His face is buried between your thighs, freckles flushed, mouth glistening, eyes locked on yours. Hungry. Possessive.
“Keep talking,” he murmurs, voice rough, lips brushing your clit. “I want to hear how good I’m making you feel.”
“You’re—you’re going to kill me,” you pant.
“I haven’t even started.”
His tongue flicks, laps, then flattens and drags in slow circles. He switches rhythms—teasing one second, focused the next. You can’t keep your legs still. One of your hands fists in his hair and tugs, hard. He groans, and the vibration makes you see stars.
“Oh yes—please—don’t stop—”
He doesn’t. He devours you like it’s the only way he’ll survive. He kisses your pussy like it’s holy. Like he’s worshipping you with his mouth. Like your pleasure is the only thing he’s ever wanted.
Your thighs start to shake. Your hands try to grip the floor.
“I’m going to—fuck—Sebastian—”
He moans, “Come on my tongue.”
It crashes through you like wildfire. Your body locks, your back arches, and you scream his name.
He licks you through it, softer now, slower, coaxing every wave of aftershock until your legs are trembling and your voice breaks.
You collapse. Boneless. Gasping.
He kisses up your thigh, your stomach, your chest, until he’s over you again.
You blink up at him, dazed. “You ruined me.”
“Now,” you whisper. “It’s your turn.”
You reach down into his boxes and wrap your hand around him.
His cock twitches against your grip. His breath quickens, eyes slamming shut as your thumb swipes across the head. When he opens them again, they’re darker than you’ve ever seen.
“Fuck,” he breathes, “you’re going to undo me.”
He kisses you hard, biting your bottom lip, hips stuttering forward like he can’t stop himself from grinding into your hand. You stroke him once, twice—just to feel him, the way he pulses against your skin.
Then your voice goes soft. “I want you inside me.”
His forehead presses to yours. “Are you sure?”
“I’ve never been surer of anything.”
Sebastian pulls back just enough to strip the rest of his clothes off—tossing his boxers to the side—and kneels between your legs again, completely bare.
You look down at him. Really look.
Not just his body—but the way he looks at you. He keeps looking at you like you’re the only thing that’s ever made sense in his fucked up world.
He strokes himself once, spreading your pussy along his length, then presses the head of his cock to your entrance. He’s slow, like he’s bracing himself for the moment everything changes.
“Tell me if it hurts,” he murmurs.
You nod, barely breathing. “I want to feel all of it.”
You gasp. The stretch is violent, unfamiliar, and so, so full.
“Y/N—” he growls, jaw clenched. “You’re so tight. So fucking warm—”
You whimper, your walls pulsing. “Don’t stop.”
He inches in deeper, watching your face for any hint of discomfort. You feel every inch of him until he’s fully inside you. When his hips finally meet yours, you moan—long and low.
“Ah—Sebastian,” you gasp. “You feel so deep.”
“Because I’m not holding back,” he murmurs. “You’re going to remember this. Every time you close your eyes.”
He stays still for a moment. Breathing. Letting you adjust.
Then he pulls out—just enough to tease your entrance—and thrusts back in. Your breath catches again. The burn is already fading, replaced with unbearable pressure and dizzying heat.
He fucks you slowly at first, hips rolling, grinding his pelvis into your clit with every stroke.
“I—I can’t believe this,” you pant.
He lowers his forehead to yours. “Believe it.”
His pace quickens. The slap of skin-on-skin echoes in the chamber. His hands grip your hips. Your moans turn to gasps. Then to curses.
“You take me so well,” he pants.
He leans back, grabs your thighs, and lifts your hips slightly—just enough to tilt your pelvis toward him. The change is subtle, but when he thrusts again—
The air punches out of your lungs.
His cock drags against something inside you that makes your entire body lock up.
Your mouth falls open but no sound comes out at first—just a strangled inhale as white heat rushes through your spine. Every nerve in your body lights up. That spot—that spot—he hits it again, and your legs jerk in response. Reflexive.
“Right there,” you moan. “Fuck—right there—don’t stop—”
You feel helpless under it. Like he’s got his hands wrapped around the base of your soul and he’s pulling pleasure out of you one grind at a time. Every deep stroke forces your body open wider. Every motion drags a desperate sound from your throat.
It’s not just penetration—it’s precision. Pressure. The perfect collision of want and anatomy and the kind of slow, focused rhythm that drives people mad.
Your thighs tremble. Your vision pulses. You can feel another orgasm building and you’re not even sure how long you’ll last.
He sees it in your face. Smirks like sin and does it again.
He’s relentless now. Slamming into you. His brow furrows, his mouth hanging open. Sweat beads at his temples, rolls down his chest. You cling to his forearms while your nails dig into his skin.
Then he grabs your wrists and pins them above your head.
“Oh, you like that,” he smirks.
“Don’t stop—don’t fucking stop—”
He thrusts even harder. Merciless.
And then he lets go of one wrist to reach down and rub your clit in tight circles.
“You’re so close,” he grunts out. “I can feel you—tightening up—fuck—come for me. Want to feel you lose it on my cock.”
Your mouth falls open. A high, broken whine slips out.
You’re already right there—so close you’re throbbing. Your body’s coiled tight, burning, clenching around him like you’re trying to drag him deeper. He keeps hitting that spot, over and over, every thrust stealing more of your breath.
“I—I can’t—” you cry out, voice wrecked. “Please, Sebastian—don’t stop—please—fuck—I’m going to—”
“That’s it,” he groans. “Give it to me. Let me feel you fall apart.”
“Please—please—want you to feel it—want you to feel how much I need you—”
Your entire body tenses around him. You scramble to grip anything to keep your body from losing control. Your thighs shake violently around his waist. Your pussy clenches down hard—dragging a groan out of him.
You can barely speak, barely breathe. You cling to him, whimpering, still trembling through the aftershocks.
“Inside,” you gasp. “Sebastian—please—want it—want you to come in me—I need to feel it—need you.”
He slams into you one last time—deep, deep—like he’s trying to put something permanent inside you.
You feel the first hot pulse of his cum, then another—thick, filling you completely. He moans your name into your neck, over and over, hips grinding through it, desperate to push every drop into you.
You’re still fluttering around him, soaked and full.
The Undercroft is finally quiet.
Your heartbeat thunders in your ears, echoing louder than the torches crackling along the walls. Sebastian lies half on top of you, still buried deep. His breath ghosts across your shoulder.
For a minute, neither of you speak.
“Are you… alright?” His voice is shaky. “I didn’t hurt you, did I?”
You shake your head. “No. You ruined me, sure. But in the best way.”
He lets out a soft, relieved sound—half laugh, half exhale—and kisses the hollow of your throat. His lips linger there like he doesn’t want to leave.
You shift, and both of you hiss—his cock twitching inside you, your thighs sticky with sweat.
“We made a mess,” you mumble.
“We did,” he agrees, smirking against your skin. “I’m proud of it.”
You let out a breathless laugh, but your body trembles when you feel him slowly pull out. You whine at the sudden emptiness. His cum leaks out of you immediately.
Sebastian watches. Then mutters, “Fuck, that’s obscene.”
He runs two fingers along your core—just to spread it wider, watch it drip out of you. You squirm.
“Stop,” you whimper, hips twitching.
“Oh no,” he murmurs. “I’m not done looking at you.”
He leans down and kisses your hip, then trails his mouth to the inside of your thigh. His tongue flicks out, tasting what he left there.
“You taste like sex,” he groans. “Like mine.”
Your legs nearly close around his head, but he pins them open. “Hold still.”
“And you let me fuck you on the floor of a cursed hideout,” he says. “What does that make you?”
“Very, very lucky,” you whisper.
He kisses your clit—just a soft brush of lips. You flinch again, oversensitive. He hums.
“You’re still so swollen.”
You glare. “That’s your fault.”
He grins. “You’re welcome.”
Sebastian crawls back up over your body, settling between your thighs again, his now-soft cock brushing against your sensitive core. You gasp—still sensitive.
“I can’t,” you say, voice shaking.
“I know.” He presses a gentle kiss to your forehead.
You wrap your arms around him, tuck your face into his neck. You feel safe there—tucked under his weight, surrounded by his warmth.
“You were incredible,” he whispers. “The sounds you made—the way you looked at me—”
You lift your head and kiss him. A different kind of hunger is there now—slower, sweeter.
“I meant what I said,” you whisper. “You’re not a monster. You never were.”
His eyes shutter. He leans his forehead to yours again. “You’re the first person to ever say that and mean it.”
“I watched everything you went through. I know what you did. But I also know why.”
“I wanted to save her. That’s all I ever wanted.”
“I know.” Your thumb strokes the line of his cheekbone. “And you deserved someone in your corner. Even if I had to fall out of the sky to do it.”
He gives a broken, hoarse laugh. “You really are mad.”
“Maybe” you whisper. “But you’re here—wrapped around me like you never want to let go.”
He eventually rolls to the side, gathering you into his arms, pulling your body against his chest. Your leg hooks over his hip. His hand drifts up and down your spine, barely touching. Just enough to feel like you’re real.
“Now…” he says, brushing hair from your face, “I memorize every inch of you. Just in case.”
“In case this isn’t real. Or in case it is, and I wake up without you.”
You pull him closer, leg tightening around him. “I’m not leaving.”
He holds you tighter. “You promise?”
You nod against his chest. “Promise.”
