
A Lesson in Mistakes | Sebastian and Ominis x Reader
You don’t realize something is wrong until the spell has already landed.
The flipendo was supposed to be countered. That was the whole point of the lesson.
You were training your students on reading intent, on recognizing the difference between a controlled spell and one that’s fueled by unchecked magic. A proper duel demands control, discipline—something you should have been watching more closely.
The fourth-year had been eager, a promising student with sharp reflexes but poor restraint. He had asked to push himself, to try something a little stronger, and you—caught between encouraging his ambition and remembering your own hunger for skill around at that age—had said yes.
You should have seen it. You should have noticed the way his grip tightened on his wand, the way his breath hitched before he cast the spell. You should have realized the instant he overcharged the charm that it was going to go wrong.
But by the time the red streak of light slammed into his opponent’s chest, sending them crashing into the stone wall with a sickening thud, it was too late.
The student didn’t get back up.
A chorus of gasping classmates, the sound of your own heartbeat pounding in your ears—all of it blurred together as you rushed to them, panic gripping your throat like a vice.
“Someone get Nurse Blainey. Now!” Your voice came out sharper than intended, but the urgency in it had the students scrambling.
The duel had not been meant to go this far. A simple exercise, that’s all it was supposed to be. The worst they should have gotten was a bruised ego or a temporary jinx—
Not this.
By the time Nurse Blainey arrived, the injured student was stirring, thank Merlin, but badly concussed, with broken ribs and a wand arm that would need of healing overnight.
Professor Hecat said nothing when she arrived, but the look in her eyes said enough.
Disappointment.
You had failed.
You don’t remember much of the meeting that followed in her office.
Only her voice, cool and measured, as she laid out the reality of the situation.
“The student will recover, but this should not have happened,” she said, her piercing eyes fixed on you. “You were meant to be supervising, not enabling. We are lucky the consequences weren’t worse.”
Each word landed like a blow, but you only nodded, fingers curling into your robes as you forced yourself to take it.
It wasn’t unfair. It was true.
“I’ll take responsibility,” you murmured, throat dry. “If the parents—if the headmaster wants me removed—”
Hecat’s lips pressed into a thin line. “No one is suggesting that,” she continued, “but you must learn from this. Errors in judgement so severe cannot be tolerated, and if you cannot handle that reality, then you must decide whether this apprenticeship is truly for you.”
She dismissed you after that.
You left the office feeling more lost than ever.
You don’t do any grading in the living room that evening.
You don’t attend dinner with the boys.
Or breakfast the following morning.
Instead, you retreat into solitude, telling yourself you need time to think, to process—to figure out if you even deserve to continue this apprenticeship.
But Sebastian and Ominis know you too well.
It starts with a knock on your bedroom door.
You ignore it, but Sebastian is insistent.
“Open the door, or I’ll use Alohomora,” he calls from the other side.
“Go away.”
The knock comes again, louder this time.
Sebastian isn’t the type to be deterred, and you know it. You bury your face in your hands, willing him to just give up, but of course, he doesn’t.
“Come on,” he presses. “Either you let us in, or Ominis gets creative. And trust me, you don’t want that.”
You hear a sigh, softer than Sebastian’s voice but no less insistent. “You could at least tell us you’re alive.” Ominis’ voice is level, but there’s something edged beneath it—concern, maybe even frustration.
You squeeze your eyes shut. “I’m fine,” you say, though the words feel like ash in your mouth.
Sebastian scoffs. “Yeah? Tell that to the fact you haven’t left this bloody room in two days.”
You don’t respond.
Another moment passes before you hear Ominis shift, his voice quieter now. “Please.”
And it’s that—the way he says it—that changes your mind.
You push yourself up from the bed, dragging yourself toward the door and unlocking it before stepping back. You don’t have the energy to do more than that.
Sebastian wastes no time. The moment the door is open, he steps inside, followed by Ominis, who moves carefully, wand in hand. Sebastian closes the door behind them and crosses his arms, looking you up and down.
And whatever he sees makes his expression falter.
Ominis, though he can’t see you, seems to sense it too.
Sebastian exhales, rubbing the back of his neck. “All right,” he says, “out with it.”
“There’s nothing to say,” you mutter, moving back toward the bed, sitting down at the edge.
Sebastian raises an eyebrow. “So you just woke up yesterday morning and decided, ‘Hmm, I think I’ll shut myself away from my two best friends, just for fun’?”
You exhale sharply, but there’s no real anger behind it.
"Sebastian, please, it's nothing."
Sebastian makes a noise in his throat, something between a scoff and a laugh, but there’s no humor in it. “Oh, it’s nothing, is it?” He gestures vaguely at you, at the way you’re slumped forward, at the dark circles under your eyes, the unmistakable tension in your posture. “You look like hell.”
You roll your eyes, rubbing your temple. “I’m just tired.”
“Bollocks,” Sebastian fires back.
Ominis, who has been standing silently at your desk, lets out a slow breath. “We’re not here to badger you,” he says, pointedly angling his his head toward Sebastian. “We just want to know what’s going on.”
You sigh and your voice comes out quieter than you intend. “Fine. I messed up at work, alright?”
Sebastian’s brows knit together, his sharp edges softening. “Messed up how?”
You press your lips together, hesitating, then finally, you force yourself to say it.
“At a duel,” you murmur. “I let a student cast something they couldn’t control.”
The words are bitter on your tongue, heavy and awful, but they keep spilling out. “I should have stopped them—I should have seen it coming—but I didn’t, and now a student is lying in the hospital wing because of me.”
A long silence follows. You don’t look at them. You can’t.
Sebastian is the first to break the silence. “That’s it?”
You blink. “What?”
“That’s why you’ve locked yourself in here for two days?”
Your fingers curl into your palm. “Sebastian, I made a massive mistake, I should have—”
“What?” Sebastian interrupts. His tone is sharper now, more serious. “Had perfect foresight?”
Your jaw tightens.
Ominis sighs, resting his hands on his lap. “Sebastian’s delivery is questionable, but he has a point,” he says. “You aren’t a Seer, and you’re not omnipotent. You’re an apprentice, and you’re still learning.”
Your stomach twists. “That’s not an excuse.”
Ominis shakes his head. “It’s reality. Nobody is perfect.”
Sebastian leans forward. “Look,” he says, his voice quieter now. “You think you’re the first professor—or near-professor—to misjudge something in a classroom? Hecat’s probably seen a hundred mistakes worse than yours. I’m willing to bet some of our professors have made worse ones too.”
You shake your head, frustration bubbling in your chest. “I’m still the one who let it happen. I should have been watching more carefully. I should have stopped it, I should have been better."
Sebastian exhales sharply, shaking his head. “Just because you messed up doesn't mean you're suddenly the worst person alive.”
Your chest tightens. You know exactly what he’s talking about.
Sebastian knows guilt better than anyone. He’s worn it, lived in it, let it consume him whole—and now, he’s watching you do the same thing.
He shakes his head. “Look, I’m not saying you shouldn’t take responsibility. But don’t sit here and act like one mistake is enough to wipe away everything else.”
You let out a breath. “Hecat said—”
Sebastian rolls his eyes. “Hecat says a lot of things.” His eyes flick up toward the ceiling before he huffs out a bitter laugh. “And look, if we got exiled from Hogwarts every time we fucked up, Ominis and I would have been gone by second year.”
Ominis tilts his head toward Sebastian. “More like you would have been gone by second year. I would have made it to fifth, at least.”
Sebastian waves a hand dismissively and despite yourself, the corner of your mouth twitches.
They both catch it.
Ominis exhales. “Do you still want this apprenticeship?”
The question startles you.
“What?”
Ominis crosses his arms. “You haven’t failed until you quit at something you still want. So, do you still want this?”
Yes. Yes, you do. You still want this.
You nod.
Sebastian claps his hands together. “Brilliant. Now, let’s get you out of here before you start fusing with the bedsheets.”
You groan. “Sebastian—”
“Nope. Up.” He stands, reaching for your arm, and tugs.
You stumble forward. “I hate you.”
Sebastian grins. “A common sentiment.”
Ominis snorts. “I’m inclined to agree.”
You roll your eyes, finally—finally—feeling something other than shame pressing down on your chest.
Because they’re right.
You made a mistake. But it doesn’t define you.
And as Sebastian drags you toward the door, loudly insisting that you owe him a drink for all this emotional labor, you think that maybe, you’re going to be okay.