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 was similar to his brother Zeus in exerting his power on women and in objectifying masculinity. He had many love affairs and fathered numerous children. Poseidon once married a Nereid, Amphitrite, and produced Triton who was half-human and half-fish. He also impregnated the Gorgon Medusa to conceive Chrysaor and Pegasus, the flying horse. The rape of Aethra by Poseidon resulted in the birth of Theseus; and he turned Caeneus into a man, at her request, after raping her. Another rape involved Amymone when she tried to escape from a satyr and Poseidon saved her. Other offspring of Poseidon include: Eumolpus, the Giant Sinis, Polyphemus, Orion, King Amycus, Proteus, Agenor and Belus from Europa, Pelias, and the King of Egypt, Busiris.
One of the most notorious love affairs of Poseidon involves his sister, Demeter. Poseidon pursued Demeter and to avoid him she turned herself into a mare. In his lust for her, Poseidon transformed himself into a stallion and captured her. Their procreation resulted in a horse, Arion. Poseidon is Greek for "Husband" (possibly of wheat), and therefore it is thought that he and Demeter (goddess of wheat) are a good match because they reign as the god and goddess of fertility.
Another infamous story of Poseidon involves the competition between him and the goddess of war, Athena, for the city of Athens. To win the people of the city over, Poseidon threw a spear at the ground and produced the Spring at the Acropolis. However, Athena won as the result of giving the people of Athens the olive tree. In his anger over the decision, Poseidon flooded the Attic Plain. Eventually, Athena and Poseidon worked together by combining their powers. Even though Poseidon was the god of horses, Athena built the first chariot. Athena also built the first ship to sail on the sea over which Poseidon ruled.
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. Poseidon is an essential character in the study of Greek mythology.