Harry Potter and the Surprisingly Competent History of Magic Professor

Cassian Rosier is a failure. A near-Squib in one of the Sacred Twenty-Eight families, he’s spent his life as the family’s punching bag... mocked, dismissed, and barely tolerated. But when a simple light spell becomes his last chance to prove himself, Cassian’s world shatters in a way none of them could have imagined. Because the Cassian they knew? He is gone. In his place is a man from another world... our world. A man with no magic but a lifetime of teaching behind him, and only the vaguest memories of a “Harry Potter” series he never bothered to read or watch. Suddenly trapped in a body with a ruined reputation and no real power, the new Cassian has one goal... to survive. When forced to give a lecture on magic, Cassian bluffs his way through by teaching Lumos... a spell he doesn’t know. But something strange happens. As hundreds of people learns from his lecture, mastery floods his mind. And then it happens again, an ancient variation of Lumos awakens, along with memories that don’t belong to him. Some memories are benign, illuminating secrets of long-forgotten magic. Others are sharp, dark, and dangerous... leaving him to wonder whether he is drawing on wisdom or inviting something far worse into himself. Now sent to Hogwarts as a professor, Cassian must juggle the expectations of his pureblood family, the suspicion of fellow teachers, and his own growing power. Every spell he teaches brings him closer to mastery... and to the ancient past that might consume him. A snarky, slow-burn power fantasy about an accidental professor who teaches magic too well, unlocks spells no one remembers, and juggles ancient memories, family politics, and students who might be the end of him. What to Expect -Light-hearted, snarky tone (Cassian’s dry humor carries the story). A reluctant but clever MC navigating Hogwarts, pureblood politics, and ancient magic. Progression fantasy elements: teaching magic makes Cassian stronger over time. Ancient spells come with lingering memories—some helpful, others unsettling. A competent teacher MC (no “bumbling fool” energy here, but plenty of witty one-liners). Slow-burn romance with a single female lead (Bathsheda Babbling). Exploration of Hogwarts daily life from a professor’s POV, with banter, levity, and political scheming. Content Warnings Mild swearing (Cassian has opinions and isn’t shy about sharing them). Family dysfunction and emotional manipulation (Rosiers gonna Rosier). Canon-typical prejudices (pureblood vs Muggle-born ideology), handled critically. Occasional darker themes tied to ancient spell memories. Slow-burn romance, no harem. No gratuitous gore or smut. Warning: May contain dangerous levels of sarcasm, accidental teaching competence, and the occasional romantic subplot you never signed up for. Proceed with tea. Disclaimer: This is a work of fanfiction created for free, non-commercial purposes. I do not own the characters, settings, or source material referenced — all rights belong to their original creators. This story is shared purely for entertainment and creative expression. I do not monetize this work in any form. It is freely available to read, and no payment is required or expected.