List of Percy Jackson and the Olympians characters
Sisyphus: A man that cheated death many times. His punishment in The Fields of Punishment was to roll a boulder up a hill. He appears in The Demigod Files in The Sword of Hades when Percy, Thalia, and Nico ask him advice. He does not really help them much, but he does say that he had helped someone else. He said that he told that other person to go see Melinoe. After that, Percy and his friends go to see her.