Neptune

Neptune is the Roman counterpart of Poseidon. As Neptune, he becomes more disciplined, militaristic and warlike than his Greek counterpart. For Greeks he was a major civic god and was highly respected for being the god of the sea and earthquakes. However the Romans, who were not seafaring people, associated him more with Fresh Water and Horses, and treated him with fear.

History
The Romans believed in a series of gods associated with world around them. They designated Neptune as the god of water and the sea, a close parallel to the Greek god, Poseidon.

As a god of both fresh water and the sea, Romans prayed to Neptune to provide water for their crops. In ancient Italy, farmers would honor Neptune with a festival in July, when frequent droughts would destroy their fields. He was also a patron of horses and had a temple called Circus Flaminius built near a race track, and another in Campus Martius.

He was also the patron of horse racing and a temple dedicated to him was situated near the Circus Flaminius which was a Roman racetrack. The Circus Flaminius was the venue for horseracing with one rider and his horse going around the turning posts. In the famous story of the Aeneid, Neptune was resentful towards the Trojans, but is not as vindictive as Juno. He was so annoyed that Juno had intruded on his domain that he helped the Trojan fleet against the efforts of Juno who tried to wreck their ships.

The Son of Neptune
He is mentioned several times during the book. He is highly feared at Camp Jupiter (by all Roman demigods in general) and his children are considered bad luck and dangerous to have around. Unlike most of the other major gods, he only has a shed as a temple, with a cobweb covered trident nailed above the door, and three dried up, moldy apples left inside as an offering. Part of the reason Camp Jupiter considers his children bad luck is because of an event in 1906, when his descendant, Shen Lun, was thought to create a major earthquake and was banished from the camp. While Percy was at Camp Jupiter, he prayed to Neptune in his temple on Temple Hill for some help.

Trivia

 * Neptune is the eighth and farthest planet from the Sun in the Solar System. It was named after the god, as its deep blue gas clouds gave the earliest astronomers the impression of great oceans and seas, the domain of Neptune.
 * In The Battle of the Labyrinth, his Greek form, Poseidon, is seen wearing a hat with the words, "Neptune's lucky fishing hat" on it.