oseidon was a son of Cronus and Rhea, and a brother of Zeus and Hades. Like his brothers and sisters he was swallowed at birth by his father Cronus but later thrown up again.
According to prophecy Cronus was to be dethroned by one of his sons but it was not known which one. Thus he swallowed or devoured all his children at birth lest one appear who would become stronger than he. Poseidon, his second son after Zeus, is described in the Iliad and Odyssey as equal to Zeus in dignity but less powerful.
The changeable face of the sea shows the changing moods of Poseidon, who became god of the sea at the same time his brothers Zeus and Hades took possession of the sky and the underworld.
Poseidon lived in a gold palace at the bottom of the sea near Aegae in Euboa. Storms abate at the approach of his chariot, which is drawn by brass-hoofed, golden-maned horses. With his trident he can stab the ground to create earthquakes, and thus has the epithet Earthshaker. Poseidon invented horses, whose gallop is like the movement of waves. He is believed to have taught men the art of managing horses by the bridle, and to have been the originator and protector of horse races.
Poseidon's violent and mercurial nature made it difficult for him to find a mate. One day he came upon Amphitrite, a daughter of Nereus, the sea god, but she fled from him. Only Delphinus (the dolphin) was able to persuade her to return to him. Thereafter, dolphins were Poseidon's favorite sea creatures, and in gratitude he placed Delphinus in the night sky as a constellation.
Once, after Poseidon and Apollo had offended Zeus, Zeus compelled them to serve haughty Laomedon, King of Troy, for a year: Apollo tended Laomedon's flocks on Mount Ida, and Poseidon built the walls of the city.
When the King refused to pay them for their work, Poseidon sent a sea monster to ravage Troy. The King was forced to offer his daughter Hesion to the monster as a sacrifice to appease Poseidon, but she was rescued by Heracles. Poseidon thus bore a grudge against Troy and sided with the Greek Army in the Trojan War.
After the war, the Greek hero Odysseus escaped death at the hands of the one-eyed Cyclops Polyphemus, a gigantic son of Poseidon, by blinding the monster with a heated stake. For this, the god of the sea delayed Odysseus' return to his homeland of Ithaca by ten years and drowned the rest of his men.
Poseidon had many children by diviniities and mortal women. In the form of a stallion, Poseidon impregnated Demeter, who was unsuccessfully raised as a mare. From their union Ariel the horse was born. The winged horse Pegasus was his son by the Gorgon Medusa. Amphritite was infuriated by Poseidon's infidelities, and turned one of her rivals, Scylla, into a voracious six-headed beast with twelve feet.(Odysseus encounters her, in the whirlpool Charybdis.) Not content with lordship over the sea, Poseidon vyed with other gods for the posession of several cities. His most famous dispute was with Athene for Athens.
Poseidon claimed kingship over Athens by flinging his trident into the ground near the Acropolis. To assert her right Athene planted an olive tree there. Arbitration was held on Mount Olympus and it was decided in favor of Athene, for whom the city was named. Poseidon's attributes are the dolphin, horse and trident. He is frequently represented in groups with Amphritite, Tritons and Nereids.