Poseidon is the ruler of the sea, often called the "Earth- shaker." After Zeus, with his brothers and sisters, defeated the Titans and dethroned Cronus, Zeus, Poseidon and Hades drew lots for one of the three realms to rule. Zeus got the heavens and thus became the supreme ruler, Hades got the underworld and Poseidon got the sea. Poseidon is very powerful, second only to Zeus himself. Poseidon had a magnificent palace beneath the sea, but spent much of his time participating in the festivities in Olympus with the other gods. Poseidon's wife is Amphitrite, granddaughter of the titan Oceanus.
Poseidon, had a very encroaching disposition, he was very dissatisfied with the his share of the world and once even conspired to dethrone Zeus. But his plot was discovered and in punishment Zeus exiled him to earth. There he was to build the walls of Troy in Anatolia for king Laomedon. He was helped by Apollo, who at the time was also banished from Olympus at that time, Apollo was able to move the heaviest of stones with just the sound of his lyre. After the task was completed Laomedon refused to reward them as promised and that was the chief reason why Poseidon was on the Greek side during the Trojan War.
Although Poseidon did give men the first horse, his primary importance was as Lord of the Sea, at his command winds rose and the most violent of storms began, but when he drove in his golden car over the water, the storms subsided and tranquil peace followed his wheels.
Both the bull and the horse are associated with Poseidon, but the bull is associated with many other gods as well, so the horse can be considered his animal. He was always depicted carrying, or using, his distinguishing weapon, the trident, a three-pronged spear which he used to shatter and shake anything he pleased.