The following days followed a rhythm. Every class started with Cassian flicking his wand and letting Lumos Spectaculum do the heavy lifting. The walls of his classroom came alive with battles, duels, rebellions, and ancient rituals. Students who came expecting another dull hour of names and dates found themselves watching history move before their eyes. Merlin arguing with Arthur, goblins clashing with wizards, witches standing at the stake with smirks, as they pretended to burn in the flames.

Once the students were hooked, he would move on. Each lesson ended with a spell… not just recited, but dissected, stripped to its bones. Cassian made them see it, feel it, build it in their heads before even touching a wand. Magicks were casting long before wands became fashionable, and he intended his students to know why. Half the time, Hogwarts taught students to memorise spells like a list of ingredients in a potions book. Cassian wanted them to understand what they were doing. He didn't want parrots mumbling Latin. He wanted them to understand… because Magicks who understood were Magicks who survived.

And it worked.

By the end of the first week, History of Magic had stopped being the school's designated nap time. Now, students actually looked forward to it. Even the ones who usually coasted through lectures sat up when the lights dimmed and Cassian let history unfold in glowing illusions. Slytherins, Gryffindors, Ravenclaws, Hufflepuffs… it didn't matter. No one liked missing class when they would be the only one who didn't see Charlemagne duel a rogue alchemist or a medieval wizard set fire to an entire castle with a single curse.

Of course, not everyone got to have fun. First-years weren't ready to be playing with fire yet… quite literally. Cassian made that clear on their first day. He wasn't their Charms professor, nor was he in charge of Defence Against the Dark Arts. That responsibility fell to Flitwick and Mulford, who would, in due time, teach them the proper way to handle magic without losing an eyebrow, or worse. Probably worse.

He told them as much, leaning against his desk as a few eager Gryffindors bounced in their seats, clearly hoping for something more exciting than history. "You lot are stuck with me for storytelling, not spellwork," he said, eyeing a particularly restless Fred and George Weasley. "I will leave the explosions to Professor Flitwick and the duelling to Professor Mulford. They get paid to make sure you don't accidentally set yourselves on fire or hex your own limbs off. I, on the other hand, don't have the patience to deal with screaming first-years running around with burnt fingers."

A few groaned in protest, but Cassian didn't budge on it. First-years weren't ready for practical spellwork beyond the basics. Until then, they would stick to history… though if they behaved, he might throw in a few illusions now and then to keep them entertained. He wasn't heartless. Just realistic.

But for the rest, Cassian introduced Incendio, the Fire-Making Charm. Six classes, four houses, hundreds of students… all given a crash course in the spell's history, application, and the reality that magic worked best when you actually understood what you were doing. The result was instant.  Incendio… Maximum Mastery. And, because things apparently weren't weird enough already, two more ancient variations landed in his lap.

Cassian sat in his quarters that evening, staring at the updated list floating in his mind.

Fire-Making Spell (Incendio)

Ancient Variant: Cinis Amissa - Instead of creating fire, this spell summons the ash of a past flame. The caster sees what was last burned in that location. Can reveal destroyed books, lost scrolls, or hidden evidence of crimes.

Fire-Making Spell (Incendio)

Ancient Variant: Pyroclave - Unlike modern fire spells that create fire instantly, Pyroclave is a delayed fire release spell that stores flames inside objects, runes, or written texts, only to be unleashed under specific conditions.

Cassian narrowed his eyes at the first one. Cinis Amissa. This... this wasn't fire. It forced fire to give up its secrets. The ashes of whatever was burned would retain the memory of what they once were, revealing hidden truths long thought lost. That kind of magic wasn't just old, it was dangerous.

His vision blurred as something pulled his mind, dragging him somewhere else. He let it take him.

A dark alley. Wet stone glistening under the dim glow of a wand. A hooded figure moving quickly, stacks of books piled in a ditch. He flipped through pages in frantic desperation before tossing them into a conjured fire. Flames swallowed parchment, curling ink into smoke. Whatever was written there… gone.

Days later, a different person stood by the same ditch. Hood drawn, wand raised. "Cinis Amissa." The ashes, long settled into filth and rainwater, glowed red. Slowly, they lifted, falling into place… not whole, no. Not even close, but enough. Pages, as incomplete as they may, hovered in the air. Letters formed meaning.

The wizard's breath hitched. A name. A date. A crime long buried was now revealed.

The wizard staggered back. Cinis Amissa didn't just summon fire… it rewound destruction caused by it, let the past bleed back into the present. A wizard could stand in a burned-down library and see every page that had turned to cinders, hear voices that had long since gone silent.

Or, in the wrong hands, erase the evidence entirely.

The vision snapped out like a flame smothered by wind. Cassian inhaled sharply, fingers tightening around his wand. Of course it had been banned. Magic like this didn't preserve history… it weaponised it. If criminals used fire to erase evidence, it meant entire histories could be rewritten. But those who knew the spell could unwrite the rewriting.

His gaze flicked back to the list.

Pyroclave.

Again, his vision shifted.

A master runesmith in a dimly lit workshop, his hands quick as he carved words into stone. Each letter glowed as he whispered the spell. "Pyroclave." The light faded, the inscription vanishing before his eyes. To anyone else, the stone was blank. But the fire was there, waiting.

Centuries passed. A thief, careless and greedy, stumbled into the abandoned ruins. His fingers traced over the old stone, rubbing at the surface as if searching for treasure.

The moment his palm rested fully against the inscription, it ignited. Fire roared to life from the once-invisible words, consuming him in a flash of heat and screaming embers.

Later, the runesmith's apprentices stood before the charred remains of their master's workshop. The knowledge was too dangerous, they agreed. It had to be destroyed. One by one, they set fire to the scrolls detailing Pyroclave, swearing the spell would die with them.

Magic designed to last. Magic that carried intent across generations.

Cassian rested his head against the back of his chair, staring at the ceiling.

What was he supposed to do with this?

These weren't just lost spells. They were remnants of something older than Hogwarts itself, magic that had shaped history before history was recorded. And now, for whatever reason, they were resurfacing.

His grip on his wand loosened.

Interesting.

***

Cassian stepped into the Headmaster's office, greeted by the sight of four House Heads already seated. Dumbledore sat at his desk, fingers steepled, while McGonagall, Sprout, Flitwick, and Snape occupied their usual spots. 

"Professor Rosier," Dumbledore greeted with a soft smile. "I trust your first few weeks have been… enlightening?"

Cassian folded his arms. "That is one way to put it."

McGonagall adjusted her spectacles. "I believe 'revolutionary' would be more accurate. I've had no fewer than twenty students tell me that History of Magic is now their favourite subject."

Flitwick beamed. "Quite right! I've seen students practicing spells from your lessons in the corridors… been years since I've seen such a genuine enthusiasm."

Snape snorted sharply through his nose. "Yes, quite the marvel. Teaching history through elaborate illusions and… correct me if I am mistaken, practical spellwork." He didn't mask his disapproval, nor his constant disdain for Cassian. "I wasn't aware the Board had hired a history professor to moonlight as a Charms and Defence instructor. Shall we all start treading on each other's subjects?"

Cassian enjoyed his expression for a few seconds, just staring, before saying, "God forbid we make history interesting. Next thing you know, students might start thinking for themselves."

McGonagall cut in before Snape could fire back. "The issue, Professor Rosier, is that your methods, while undeniably effective… blur the lines between subjects. First-years expect spellwork in their History classes, and while I appreciate your enthusiasm, it does complicate matters."

Cassian smiled lightly, he long knew his methods would raise some questions, "I assure you all, my intention is to teach and nothing more. I know my appointment here isn't exactly based on merit, and I understand the concerns that might raise. But I take my responsibilities seriously."

McGonagall studied him over the rim of her glasses. "That much is clear."

Sprout nodded. "More than clear. You've managed to make a subject students usually sleep through into something they actually talk about outside of class. I hear about your lessons in my greenhouses more than I do about actual Herbology."

Snape gave another snort. "Yes, truly groundbreaking. I imagine Flitwick and Mulford are thrilled to have a History professor who fancies himself a Charms and Defence instructor as well."

Cassian didn't bother looking at him. "I don't teach them anything they haven’t already covered in their Charms or Defence classes. I only step in once the spell is familiar, to show them where it came from, how it is changed over time, and why it mattered. I am not getting ahead of anyone, I am filling in what gets left out."

Snape's lip curled slightly, but Dumbledore cut in before he could say more. "Professor Rosier, would you mind giving us a demonstration? I admit, I am rather curious myself."

Cassian leaned back in his chair. "Any requests?"

Dumbledore's smile deepened. "Surprise us, Professor Rosier. That does seem to be your speciality."

Spoiler

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