Poseidon is a god of many names. He is most famous as the god of the sea. The son of Cronus and Rhea, Poseidon is one of six siblings who eventually "divided the power of the world." The division of the universe involved him and his brothers, Zeus and Hades. Poseidon became ruler of the sea, Zeus ruled the sky, and Hades ruled the underworld.
Poseidon was relied upon by sailors for a safe voyage on the sea. Many men drowned horses in sacrifice of his honor. He lived on the ocean floor in a palace made of coral and gems, and drove a chariot pulled by horses. However, Poseidon was a very moody divinity, and his temperament could sometimes result in violence. When he was in a good mood, Poseidon created new lands in the water and a calm sea. In contrast, when he was in a bad mood, Poseidon would strike the ground with a trident and cause unruly springs and earthquakes, ship wrecks, and drownings.
Poseidon often used his powers of earthquakes, water, and horses to inflict fear and punishment on people as revenge. Though he could be difficult and assert his powers over the gods and mortals, Poseidon could be cooperative and it was he who helped the Greeks during the Trojan War.