Charybdis

Charybdis is a monster in the Percy Jackson and the Olympians series, appearing in ''The Sea of Monsters. ''

History
Charybdis was once a beautiful sea goddess and the daughter of Poseidon and Gaea. However, she was turned into a vicious monster that created a whirlpool and sucked in passing ships, and began acting as guardian for the sea of Monsters. She and her "sister" Scylla guard the Sea of Monsters.

The Sea of Monsters
Clarisse La Rue was on a mission to retrieve the Golden Fleece, but she and her crew were sucked into Charybdis after Clarisse's satyr companion confronted Scylla and was killed by her. Percy, Tyson and Annabeth later encounter Charybdis and are sucked into the monster's stomach, where they are reunited with Clarisse and her crew of Confederate Zombie soldiers. Both Clarisse and Percy managed to escape.