Iapetus

"His name means "The Piercer," because that's what he likes to do to his enemies."

- Thalia Grace

Iapetus (in Ancient Greek: Ιαπετός) is the Titan of mortal life, the brother of Kronos, the father of Atlas, Prometheus, Epimetheus, and Menoetius by Clymene.

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

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.

Offspring
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 is a guileless fool, Atlas is overly daring, and arrogant Menoetius is 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 Sword of Hades
"I'm sure my brother Kronos will reward you. But now we have killing to attend to."

- Iapetus to Ethan Nakamura

Iapetus is first introduced as an enemy of the gods. He battles Percy, Nico, and Thalia; and appears to be winning, but Percy grabs Iapetus with the little remaining strength he has in his injured arm and pulls himself and Iapetus in the River Lethe, which is able to wipe out a person's memory. When Iapetus comes out, Percy convinces him that his name is "Bob" and that they were good friends. "Bob" notices Percy's wounded arm and grimaces "owie" and heals 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 do.

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

The Lost Hero
He is indirectly mentioned by Annabeth Chase while she and Jason Grace were in the Hypnos' Cabin.

Appearance
Iapetus wore a tattered orange prison jumpsuit, has gray hair that sticks up in every direction, a scraggly beard, pure silver eyes, and is very thin and haggard and is said to be 10 feet tall.

Trivia

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