Harry Potter and Mischief System
Adam Wright, an 11-year-old orphan, awakens in 1991 with transmigrated memories proving the Harry Potter world is real and desperately escapes St. Catherine's to reach Platform 9¾.
Rejected by the solid barrier and cursed with gibberish that turns his revelations into nonsense, he crashes in pain as guards haul him away.
Dumbledore invades his mind, senses "wrongness," and fails an Obliviate, awakening the Mischief System: HP/MP/SP stats, a shop for wandless spells with prank side-effects, and missions enforcing Robin Hood ethics.
Adam flees to London's streets, survives via chaotic thefts from the corrupt, buys Lumos for his first tearful magic, and over two years levels up through heists.
Forging a false identity, he infiltrates Hogwarts as a Slytherin in 1993, forms wary alliances with Daphne and Harry's trio, masters advanced Patronus amid Lupin's probes and Hermione's investigations, all while hiding from Dumbledore to expose wizarding corruption from the shadows.