1Sing o Muse of the Rage of Perseus Son of Neptune » AU Percy is a Roman demigod and the son of Neptune rather than Poseidon. At the start of The Lightning Thief Percy is 14 years old rather than 12, and the great prophecy occurs at 18 rather than 16. The pairing is Percy x Bianca. The aesthetics are more serious, deaths are gorier (Monster and Mortal), the world is more dangerous. However, Percy will remain his usual upbeat self.