Amphitrite

"This is my, er, wife, Amphitrite."

- Poseidon

Amphitrite (Αμφιτρίτη in Ancient Greek) is the immortal wife of Poseidon and Queen of the Sea. She is sometimes listed among the Oceanids, but more often she said to be one of the fifty Nereids, daughters of the Sea god, Nereus and the Oceanid, Doris. By Poseidon, she is the mother of Triton. Her Roman counterpart is Salacia.

History
After Poseidon replaced her grandfather as ruler of the Sea, Amphitrite became his wife. When she resisted she tried to run away to her brother for help (usually Atlas) Poseidon sent a dolphin to retrieve her. They had a son, Triton, who became both his father's heir and herald.

Appearance
"To his right stood a beautiful woman in green armor with flowing black hair and strange little horns like crab claws."

- Percy Jackson

Amphitrite is a beautiful goddess, with flowing black hair and small horns like crab claws.

Personality
"Excuse me, my lord. I am needed in the battle."

- Amphitrite Amphitrite is a formal goddess, calling her husband "my lord." She is proud and haughty to Percy, but is likely otherwise when she is speaking to others. She seems hurt by her husbands' liasons, and probably wasn't happy when Poseidon broke his promise on the River Styx that he wouldn't have anymore demigod children, resulting in Percy whom it seems Amphitrite will never forgive. In myth, she does not, like Hera, punish or harm her husband's mistresses or his children by them, but she does show strong disapproval and disdain for Percy.

The Last Olympian
Amphitrite is seen talking strategy with her husband Poseidon in the throne room of their ocean floor palace, along with their son, Triton. Percy Jackson, her stepson, joins them, and Amphitrite treats him coldly, as he is the proof of her husband's unfaithfulness. Percy expects nothing else, and feels sorry for her as she doesn't have a faithful husband. She is worried how Oceanus is attacking and how Poseidon is losing power to the former ruler of the Sea. She is shown as a warrior, as she leaves the meeting to return to the battle.

Trivia

 * Her Roman Counterpart is Salacia, goddess of sea water.