Keto

Keto (also spelled Ketos, Ceto, or Cetus) (Ancient Greek: Κετο) is one of the most powerful ocean monsters in Greek mythology. She was mentioned by Chiron in The Titan's Curse, and also appears as one of the antagonists in The Mark of Athena.

Description
Keto is the daughter of Pontus and Gaea. She is most notable for bearing by her husband as well as her brother Phorcys, an old sea god, The Gorgon sisters Medusa, Euryale, and Stheno, at the same time Phorcydes the Graeae (Graiai), also known as the Gray Sisters, Echidna, and Ladon.

History
The Queen of Äthiopia, Cassiopeia, once said she would be more beautiful than the Nereids. Angry because of this, Poseidon sent Keto to cause trouble in Äthiopia. To calm Keto it was decided to sacrifice Cassiopeia's daughter Andromeda. She was chained to rocks and had to see as Keto came closer. Before the monster struck, Perseus appeared at the cliff and fell in love with Andromeda with one look. Andromeda told him that she had begged her fiance to rescue her but, cowardly, he left. Perseus killed the monster and brought Andromeda to safety. Promptly he asked Andromeda's parents for her hand. Her parents promised him not only Andromeda, but the whole kingdom, for they were grateful for the life of their daughter.

There are a few different versions of the way Perseus killed Keto. In one version he showed Keto the head of Medusa, so that Keto turned into stone.

There was also Keto Trois, also called Trojan Sea Monster.

The Mark of Athena
While Percy Jackson, Frank Zhang, and Gleeson Hedge are waiting outside the Georgia Aquarium to hopefully meet Phorcys for information, they all reach into their pockets to see if they have any money to pay for entry. Frank only has three denarii, which a girl quickly scoops up and says that it is the right payment for the VIP tour. While the group feels that this is most likely a trap, they follow the girl into the aquarium and find that her name tag says Kate. As Kate gives them the tour, she seems excited about the larger animals and gives the group very detailed information, but is uninformed about the smaller creatures (calling some fish in a tank the "yellow ones").

As they pass by a gift shop, Kate tells them to take anything they want. While Percy is a bit reluctant, Frank starts to take a few shirts as he hadn't packed for a long trip, a snow globe, and a Chinese finger trap. As the group go farther into the aquarium, Kate begins to reveal she knows a lot about the group, including that Hedge was a satyr. As they look at the whale sharks, Kate tells them that they should see some of her babies out in the wild. When Percy questions if she knows Phorcys, she explains that he is who they are going to see, along with some of the really big exhibits. As they enter the Death In The Deep Seas! exhibit, Kate explains that she tried to teach some of the creatures in the tanks tricks (including a pair of Nereids), but with no luck. Percy starts to feel uneasy as Kate casually talks about sedating some of the sea creatures, even two Telekhines.

Percy becomes really nervous however when Kate shows that she already knows he is a son of Poseidon. When Percy asks her what the name "Kate" stands for on her name tag, she is momentarily confused and reveals her name is actually Keto and the name tag is a misprint. When Phorcys enters the room, Keto informs him about the misprint, as his name was changed to Porky. Phorcys criticizes her for a moment, telling her that entertainment is more important than education. Coach Hedge however wants to hear more and Keto takes him down a hallway to show him a few more creatures, leaving Frank and Percy with Phorcys.

After Phorcys captured the two demigods in one of his special tanks, Keto walked past the glass with Coach Hedge. They manage to alert Gleeson that the are trapped, resulting in the satyr kicking Keto in the back of the head, knocking her out. Gleeson then helped free Frank and Percy before escaping. Keto was so angered by this, that she sent Skolopendra after the group. Keto posed as an employee in a Georgia Aquarium named Kate.

Personality
Keto has a somewhat bubbly personality. She is incredibly fond of large sea creatures, but has little knowledge of smaller animals. She enjoys sharing her knowledge with anyone that will listen to it and has a habit of bouncing around on the balls of her feet, as if having problems containing her energy. Despite being the mother of sea monsters, she seems to be unfeeling toward of forms of life, casually talking about sedating other sea creatures on display and trying to teach them tricks. She is also somewhat vengeful, as she sent Skolopendra after the crew of the Argo II after they defeated her.

Appearance
Keto appears at first as a worker for the aquarium, appearing to be in her twenties. She has frizzy black hair, which she pulls to the side in pigtails. She has dimpled cheeks, braces, and think-framed glasses, which makes Percy think she looks like a school girl. She wears a Georgia Aquarium polo shirt with dark slacks and black sneakers.

Keto in Ancient Texts
It is said that Keto had children with Phorcys, as Echidna, the Gorgons (Medusa, Euryale, and Stheno and sometimes Scylla), and Ladon are their offspring. It is also said that Typhon is Keto's grandson.

Trivia

 * In The Lightning Thief (film), when Percy was asked by Chiron if he knew any other demigods, he looked at a mural with the name Perseus defeats Cetus, and thus knew the answer.
 * The asteroid 65489 Ceto was named after her and it's satellite after her husband.
 * Alternatively with the Ketos killed by Perseus, there was also Keto Trois, killed by Herakles.
 * Like Typhon being the most powerful Storm Monster, Keto is considered to be the most powerful Ocean Monster.
 * Keto is seen in The Mark of Athena. At first they think her name is Kate because of the name tag company error.