Poseidon

Poseidon, Neptune in Roman form, is the god of the sea, earthquakes and horses in Rick Riordan's books and the brother of Zeus and Hades. In The Lightning Thief he is suspected of stealing Zeus's master bolt with Percy's help, nearly starting a war, until Percy wins it back from Ares and returns it. He later invites Tyson to work at his underwater forge, fights Oceanus under the sea during the Second Titan War, and joins the battle against Typhon once Percy convinces him he is needed. He fights the Giants in the Second Gigantomachy and names Kymopoleia as his daughter. His cabin at Camp Half-Blood is Cabin 3, where Percy is the only permanent resident. Kevin McKidd plays him in the film and Toby Stephens in the TV series.