Characters in The Sea of Monsters

Percy Jackson

Also in The Lightning Thief, The Titan's Curse, The Battle of the Labyrinth, Percy Jackson and the Sword of Hades, The Last Olympian, Percy Jackson and the Singer of Apollo, The Chalice of the Gods, Wrath of the Triple Goddess, Percy Jackson's Greek Gods, Percy Jackson's Greek Heroes

Polyphemus

The Cyclops guarding the Golden Fleece on his island.

Luke Castellan

A traitorous demigod serving the Titan lord Kronos.

Annabeth Chase

Also in The Lightning Thief, The Titan's Curse, The Battle of the Labyrinth, The Last Olympian, The Chalice of the Gods, Wrath of the Triple Goddess, The Demigod Files

Tyson

Cyclops revealed to be Percy's half-brother.

Also in The Battle of the Labyrinth

Clarisse La Rue

A tough daughter of Ares sent on the official quest for the Fleece.

Also in The Last Olympian, The Demigod Files

Grover Underwood

Also in The Lightning Thief, The Battle of the Labyrinth, The Last Olympian, Percy Jackson and the Singer of Apollo, The Chalice of the Gods, Wrath of the Triple Goddess