Poseidon was a god in Greek mythology who ruled the realm of the sea. In Roman mythology, Poseidon is called Neptune, but the characteristics are the same.
Origins
Poseidon was one of the ruling gods of ancient Greece, son of titans Cronus and Rhea, and brother of Zeus, king of the gods. According to one version of the myth, Poseidon's father swallows him at birth. He survives this to become god of the sea. Another version disputes this, saying Poseidon and his brother, Zeus, were not swallowed by their father like their brothers and sisters. In this version, his mother hid him in Rhodes, where he was raised.
God of the Sea
The Iliad states that the three brothers--Zeus, Poseidon and Hades--divided up the three realms of the universe. Zeus received the sky. Poseidon chose the sea and Hades took the underworld. Poseidon controlled the ocean and its creatures and was also capable of creating strong earthquakes on land.
Followers
Poseidon was worshiped in many cities and by sailors. Sacrifices were made in his name to ask for smooth weather conditions for sailing. Poseidon could use his trident as a weapon to whip up storms, cause earthquakes and engineer floods. Poseidon's early responsibility was the Oracle at Delphi before it became Apollo's duty.
Children
According to Greek mythology, Poseidon fathered more than 50 children. The mothers ranged from human to goddess. While some of the children were human, other progeny include horses, giants, a cyclops and a merman (male mermaid).
The Myth
As an immortal, he could never die. While there are stories of his exploits, there is no record of his actual death. He was never considered to be someone who was capable of dying. Greek and Roman worship of Poseidon and the other gods died off as Christianity emerged.
While it is possible to say that Poseidon and the other Greek gods died symbolically when they faded into history and ancient myth, there is no way to pin down a time or date of "death."
Poseidon and the other gods of Olympus simply faded into memory with the growing interest in Christianity.
