List of Percy Jackson and the Olympians characters
Kronos: The Lord of the Titans and the main antagonist of the series. He tries to get Percy to join him and fight against the Olympians. His weapon is a  sword named Backbiter remade into the scythe. He is the father of the "Big Three," which are Zeus, Poseidon, and Hades. He is also the father of Demeter, Hera, Chiron and Hestia. He was sent to Tartarus by his sons and is reforming in The Sea of Monsters, The Titan's Curse, and The Battle of the Labyrinth. When he eventually reforms himself, he takes Luke as his host body. The only reason Luke was not killed during this was because he bore the Curse of Achilles. In The Battle of the Labyrinth, Kronos is delayed to attack Camp Half-Blood. In the fifth book, Kronos leads the Titans to Olympus while the gods were fighting with Typhon. Later, Annabeth and Percy save Luke, and Luke sacrificed himself to defeat Kronos.