Poseidon (Greek) / Neptune (Roman)
God of water and the seas. Neptune was considered less important, most likely because the sea was not as sacred to the Romans as it was to the Greeks.
Poseidon gained control of the seas in a game of lots to divide the universe among he and his brothers, Zeus and Hades. The Cyclopes gave Poseidon a magic trident, which made his shows of power even more terrifying. The waves crashed all around, and he even caused earthquakes.
Poseidon lived in the Aegean Sea in an underwater castle, and traveled in a chariot pulled by imperial seahorses. One day, Poseidon decided to challenge Zeus' authority with the help of the goddesses Athena and Hera. He planned on binding Zeus up, but was stopped immediately by the monster with a hundred arms, Brareus, whom Zeus had called up from Tartarus to preserve his safety. Poseidon's offspring also had bad temperaments. Polyphemus, his son (and a Cyclopes), was known for devouring a few of Odysseus' followers. Odysseus barely escaped with the help of a heated stake by blinding Polyphemus. Poseidon was not eager to exonerate Odysseus of the incident.