Iapetus

Iapetus (or Iapetos) is the Titan of mortal life and the brother of Kronos and the father of Atlas, Prometheus, Epimetheus, and Menoetius by Clymene. His name means The Piercer, because that's what he likes to do to his enemies, as said by Thalia Grace. Iapetus was the former ruler of the Underworld and was cast into Tartarus after the war along with his brothers. Being the Titan of Mortal-Life (or rather the mortal life span), his sons Prometheus and Epimetheus were represented as the creators of mankind and other mortal creatures. His last son Menoetius was the Titan of Rash Action. He was said to be the Pilar of the West.

History
He and three of his brothers were posted at the four corners of the world (Iapetus in the West) where they seized hold of the Sky-god and held him fast, while Kronos, hidden in the center, sliced him up with a sickle. Iapetus' position as a pillar of the West was later taken up by his son Altas

Offsprings
The sons of Iapetus were also described as possessing some of the worst of human traits: mostly on an intellectual level, Prometheus is overly sly and crafty, Epimetheus a guileless fool, Atlas overly daring, and arrogant Menoetius prone to rash and violent actions. Their natural traits led each to their downfall. Iapetus and his family were regarded as the ancestors of mankind, a race which inherited the worst qualities of these four sons: crafty scheming, foolish stupidity, excessive daring, and rash violence.

The Demigod Files
Iapetus is first introduced in The Demigod Files as an enemy of the gods. He battles Percy and appears to be winning, but Percy grabs Iapetus with the little remaining 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 was "Bob" and that they were good friends. "Bob" noticed Percy's wound from the Keres (daimones) and healed it with just a touch. When Percy confronts Persephone about the sword, Percy threatens to toss her in the River Lethe with Bob's help, which Bob gladly agrees to.

Iapetus is later said to be given a job in the Underworld, for the good of the Olympians this time.

Appearance
Iapetus wore a tattered orange prison jumpsuit, has gray hair that stick up in every direction, a scraggly beard, pure silver eyes, and is very thin and haggard (in his first and only appearance in the series so there might be some differences later). In The Demigod Files he was said to be 10 feet tall.

Trivia

 * Iapetus, the third largest moon of Saturn, is named after him.