Calypso

Calypso (also known as Atlantis in Greek Mythology, Ατλαντίδα in Ancient Greek) is a character who appears for a brief time in The Battle of the Labyrinth. She is described as being, kind, down to earth and even more beautiful than Aphrodite.

History
The Greek mythological Calypso is described as a lovely seductress. Odysseus finds his way to Ogygia, where Calypso keeps him because she loves him. After bearing him two sons, she dies of a broken heart when Odysseus leaves.

The Battle of the Labyrinth
Calypso found Percy on the shores of Ogygia after he caused Mt. Saint Helens to erupt. Percy at first was unsure of her as she and the island were both very beautiful, and in his experience, places like that are usually traps. She did admit that she was the daughter of Atlas, but said she wouldn't hurt him. She healed him and let him roam around the island. One night when they were eating dinner Percy asked her why she always pulled away and teared up when she looked at him and refused to enjoy herself. She was about to tell him when Hephaestus showed up. He told them what was going on back in civilization and left after a short time. Percy then remembered that he had to go back to camp Half-Blood. Calypso was saddened by the news and explained to Percy that she was cursed to stay on Ogygia forever by the Gods, because she supported her father in the first great war. She is also cursed to have heroes wash up on her island, wounded or hurt, for her to heal: she must always fall in love with them, but they must always leave. She offers Percy the chance to stay with her on Ogygia, where he would be immortal. Though Percy hated to refuse, he did, because his friends needed his help. Accepting his choice, Calypso makes him a magical raft and sends him off, asking him to take one of her flowers and plant it in Manhattan, which he did at the end of the book, and which later appears again in his windowsill in The Last Olympian.

The Last Olympian
At the end of the book Percy makes a request to the gods that Calypso, along with any other peaceful titans who did not fight in the original war be allowed amnesty and be freed pointing out that their treatment by the gods was what caused some of them to switch sides. It can be presumed that Calypso is now free.

Calypso is also mentioned when Prometheus asks Percy to surrender.