Iapetus

Iapetus was the main antagonist of the short story The Sword of Hades. In the story, Iapetus utilizes demigod Ethan Nakamura to help him steal the titular sword of Hades and escape from Tartarus. He is apprehended by a team of three heroes, Percy Jackson, Thalia Grace, and Nico di Angelo. In the struggle that ensued, Percy knocks Iapetus into the River Lethe. With his memory erased, Percy convinces the Titan that he is an ally of the Olympians, Bob.

Bob next appears in the fourth installment of The Heroes of Olympus series, The House of Hades, as a secondary protagonist. Throughout the book, Bob struggles with his two identities, the villain Iapetus and the hero Bob. As his memories are fully restored, Bob finally decides to be more than Iapetus and he sacrifices himself to help Percy and his girlfriend Annabeth Chase close the Doors of Death and defeat Gaea.

Trivia

 * Iapetus is similar to Darth Revan in the fact that both villains became heroes after their memories were stolen.