Perseus "Percy" Jackson is a son of Poseidon and is the protagonist and narrator of the series. Being a child of one of the "Big Three" (Zeus, Hades, Poseidon), Percy is the hero referred to within the prophecy of the Oracle, which foretells that the next half-blood child of the "Big Three" to reach the age of sixteen would have to make a decision that would mean the destruction or saving of Olympus. He also is called “Seaweed brain”, especially by Annabeth.