To borrow

When a letter arrives for unhappy but ordinary harry potter, a decade-old secret is revealed to him that apparently hes the last to know his parents were wizards, killed by a dark lords curse when harry was just a baby, and which he somehow survived escaping his hideous muggle guardians for hogwarts, a wizarding school brimming with ghosts and enchantments, harry stumbles upon a sinister adventure when he finds a three-headed dog guarding a room on the third floor then he hears of a missing stone with astonishing powers which could be valuable, dangerous, or both