Iapetus

Iapetus is the brother of Kronos and the father of Atlas. His name means "The Piercer", because that's what he likes to do to his enemies, as said by Thalia in "The Sword of Hades" in The Demigod Files. He battles Percy, and Percy grabs Iapetus with the little strength he had in his injured arm and pulled himself and Iapetus in the River Lethe, which makes you forget everything about yourself. When Iapetus came out, Percy convinced him that his name is "Bob" and that they are good friends.