CASS42- Eureka

It was mid January when Marius Vale, freshly appointed Defence Against the Dark Arts professor and walking midlife crisis, bolted down the main staircase with no clothes, no dignity, and no intention of explaining himself.

"Eureka!" he shouted... though not the jubilant sort. This was the kind you screamed when you just seen your own spleen crawling across the ceiling.

A magical blur trailed behind him, covering his whatnots. Not a spell, more like a hasty clean-up squad, probably conjured by Hogwarts' preservation instinct. Or McGonagall. Possibly Dumbledore. Maybe all three.

By the time he hit the front doors, the blur had wrapped him in what looked suspiciously like a tablecloth. Then he was gone. Vanished into the snow like a ghost no one had requested.

Cassian, having witnessed all this from the upper staircase, biscuit halfway to his mouth.

"Right then." He bit into his biscuit maybe ten minutes later. "This place is nuts. Not the best wording probably."

Turned out, as Cassian predicted, Vale had been trying to lift the curse on the Defence Against the Dark Arts position. Thought he could brute-force it, crack the enchantment with a hybrid ritual-slash-breakdown. He went barking before the spell broke. Ran through the halls with all the confidence of a man whose brain had started leaking out from the ear. Naked.

It was a miracle, all of it happening late at night, with no student around to bear witness.

Word was, Dumbledore had sent word to an old student... Olivia Green. Used to be sharp, top of her class, disappeared into the Department of Mysteries straight after graduation. Most of the staff hadn't heard her name in years. Now she was called back. Apparently, she said yes without blinking.

The announcement came down two days after Vale's streaking incident. McGonagall gathered them in the staff room, face pinched tighter than Snape's budget for conditioner.  No one had the nerve to ask, but Cassian would've bet half a chocolate frog she already downed a calming draught beforehand.

McGonagall asked if anyone wanted to hold the post until a new professor arrived. Predictably, the room responded with the sort of silence usually reserved for funerals. 

Snape raised a hand.

He didn't look at anyone. Just sort of... hovered there, pale fingers lifted like he was volunteering to dissect something already half-rotten. His eyes were fixed on the opposite wall, probably imagining all the curses he could teach first-years if given a week of freedom and no supervision.

Cassian watched Dumbledore from the corner of his eye. The old man just sipped his tea, smiled vaguely, and said no.

And that was that. Two days of no class. Students roamed the corridors with the kind of gleeful chaos that made Cassian consider investing in tranquiliser charms. Some were convinced they'd been cursed by Vale's leftover madness. One third-year named Tom, claimed his mirror was whispering marvels and riddles. Cassian told him that was puberty.

The new professor arrived on the third day. Walked in just before breakfast, dragging a battered trunk behind her. She parked it by the staff table, then turned and surveyed the Great Hall like she was checking for structural flaws.

Snape didn't even wait until pudding. He was scowling by the time the butter hit her plate. She introduced herself to the students by first name only. Olivia. Said she would hex anyone who called her Professor or Green... either she hated the name or the concept of hierarchy. Possibly both.

That was the highlight of the second semester. The rest unfolded exactly as it should've, quiet by Hogwarts standards, which meant barely one fire a week and no confirmed fatalities. Cassian carried on in his usual way, which involved scaring first-years half to death with unscheduled quizzes and correcting centuries-old textbooks with petty footnotes. He still ran his classroom like a cross between a spell library and a poorly supervised museum exhibit.

Students didn't always understand him, but they remembered his teaching... which, really, was half the job done.

The rest of the year blurred together in a chaos of essays, misfired spells, and questionable facial hair decisions. Cassian still sprinkled a bit of spellwork into historical case studies, push them to think like cursebreakers instead of parrots, and, in the process, earn himself another mastery and maybe unlock a forgotten charm or two. Not bad for a man juggling a classroom, a traumatised metamorphmagus, and a girlfriend who used sarcasm as a breakfast condiment.

That is how he got Apertis Oculus.

It wasn't flashy. No divine thunder or ghosts whispering secrets into his ear. It happened on Valentine's Day. The corridor outside was half-flooded because someone had enchanted the suits of armour to cry every time they heard a love song. Inside, Cassian was elbow-deep in the curriculum, eyes halfway closed as he scribbled notes and tried to figure out if it was worth getting in a fight with the Ministry over their insistence on rewriting the Troll Wars to make the wizards look heroic.

The memory appeared without a warning. One moment, he was staring at the page, the next, the world flickered.

Text rushed across his vision.

Ancient Variant Unlocked: Apertis Oculus

Condition Met.

Apertis Oculus - Older unlocking charm. Affects magical concealment. Forces passage by disrupting both enchantment and obfuscation layers. Duration: Temporary. Strain: Moderate.

A second later, he wasn't in his office anymore.

The air changed first, thick, cold, the kind of damp that soaked right into your teeth. Light slipped in through a crack high up in the stone, a slit window barely wide enough for a finger. It was a tomb. Or something similar. The ceiling arched like a cathedral. Dust floated in the air like snow, frozen mid-fall.

There was a door ahead. Not a regular door, stone sealed, symbols cut into the frame like scars. No handle. No hinges. Just a solid wall.

Cassian, no, the host, stepped closer. Wands didn't exist yet. Just hands. The memory raised a palm, fingers curling like it meant to knock. Then she spoke.

Something old. Rooted in syllables that felt like carved bone and old thunder. The spell pulsed, and the door cracked.

A seam split down the middle. Light bled through, green-gold. The entire passage was a lie. Illusion layered over enchantment, a lock stitched into the wall of reality itself. The spell peeled it back.

Apertis Oculus wasn't an unlocking charm. Oh no, it was not. It was an unveiling. Peered through the curtain and yanked it down if you stared long enough.

He didn't get much further. The memory snapped and the vision ripped away.

 That was it.

When the year wrapped, Slytherin banners were decorating the Great Hall again. Snape looked smug. Not that it was new. But this time he had reason, and unfortunately, so did his eyebrows.

Cassian didn't bother grumbling about it. He hardly cared. Slytherin played the long game... shady study groups, suspiciously successful duels, and a frankly impressive ability to avoid getting caught mid-prank. They deserved the win, probably. Still, didn't mean he enjoyed seeing Odette's smirk reflected in every corner.

After the feast, Tonks hugged them both like she was trying to break something. Tight around the ribs, head shoved into Cassian's chest, arms looped round Bathsheda's side like she wasn't quite ready to let go. She cried a bit. Not ugly sobbing, more like the kind of dignified leak. Cassian patted her head with one hand, the other still holding his tea.

"You gonna be fine, kiddo."

She made a wet snort into his shoulder. "I still feel like my bones are itchy."

"Sign of progress," he said. "Also possibly internal bleeding. Either way, very magical."

She groaned and didn't let go.

"Hey," he muttered, nudging her with his knuckles. "You are not dying. You are graduating."

"That is worse."

"No, worse is coming back here as staff. We would be colleagues."

That got a grunt from somewhere near his ribs. "I would poison your tea."

She finally stepped back, wiping her face with the sleeve of her jumper. Red nose, blotchy cheeks, a half-melted mascara streak across one eye. She looked like she'd been emotionally mugged.

"Try not to miss me too much," she said, sniffling.

Cassian tilted his head. "We will try. But I make no promises on mocking your dramatic exits."

Tonks sniffed again, rubbed her eyes. "I am serious."

"You are Nymphadora. Always have been."

She hissed like a kettle. "You absolute bastard."

Cassian beamed. "She is back."

Bathsheda leaned over and pulled Tonks into another quick hug. Less spine-breaking this time. More swinging.

"You will be fine, I sent some letters to my friends." she said quietly.

She thanked, then left without another word. Cassian didn't watch her go. He just stood there a moment, rubbing his palm along his jaw.

"Alright," he said. "Now I feel old."

"You are," Bathsheda muttered, already returning to her notes. "You are a fossil. A sarcastic one."

"A relic," he said. "Very valuable. Probably cursed."

"No probably about it."

The staff dinner arrived, Cassian showed up ten minutes early. Cassian slid into the chair beside Bathsheda, muttered, "You look nice," and nicked a bread roll from McGonagall's side plate when she blinked.

Most of the night passed in dull chatter. Something about new Ministry guidelines, something else about Hogsmeade zoning. Cassian nodded along, eyes dropping. Someone mentioned ward inspections. He nearly threw his fork.

Midway through pudding, Dumbledore clinked a spoon against his glass. The table stilled. He stood, twinkle mildly weaponised.

"Another year gone," he said, smiling over his half-moon spectacles. "And one, I think, we can call… educational."

Cassian whispered, "Revolutionary."

Bathsheda kicked him under the table.

"And of course," Dumbledore went on, "a warm goodbye to Professor Olivia Green, who, despite her wishes, will be addressed formally at least once a year, by contract and tradition."

Well, smart lass signed her resignation before the year ended, lest she was struck by lightning. Turned out, that was an effective method to dodge the curse. A rare success story in a position that ate more professors than Peeves ate sugar quills. She cleared out before the end-of-year feast, didn't even take the pudding. Left behind a single note on the staffroom noticeboard, "Survived. Not returning. Don't send flowers."

Cassian framed it.

Bathsheda caught him with it a few days later, trying to find the right spot over his desk. She didn't ask. Just gave him a look that said, "You are the worst," and went back to her academic stack. He added a tiny garland around it. Festive.

With Olivia gone, the post opened again. Dumbledore, in all his glitter-dusted wisdom, didn't fill it right away. Claimed he had "candidates." Didn't say from where. Didn't say when. Knowing him, probably kept them in a jar somewhere until the term turned interesting.