Charybdis is a minor antagonist in Percy Jackson and the Olympians: The Sea of Monsters, the second installment of the Camp Half-Blood book series. She is a former giantess who was the daughter of Gaea and Poseidon and therefore the half-sister of Percy Jackson. She was turned into a monstrous whirlpool that lives in the titular sea alongside Scylla.
Background[]
She was once a beautiful giantess daughter of Poseidon and Gaia, aiding her father in his bitter rivalry with Zeus. Enraged, her uncle transformed her into a terrifying monster for all eternity. She lives in the titular seas and literally eats any passing ships that near her waters, causing a series of whirlpools around the world. While she lays on one side of the narrow channel, the monster Scylla was within an arrow shot. Sailors attempting to avoid Charybdis will pass too close to Scylla and vice-versa.