In Fall of the Trident Setna is an Egyptian high priest allied with Amanra. He helps Arkantos resurrect the god Osiris. Setna is the only character in the game who is a real historical character. Setna Khaenwaset was a son of Ramesses the Great, and was indeed a priest and magician. He was the High Priest of Ptah (as opposed to Osiris in the game), and is known for his restoration of the Apis cult, the restoration of the Pyramid of Unas, and his search for the mystical Book of Thoth. The reign of his father, Ramesses, has sometimes been portrayed as around the same time as the Trojan War, so Setna's appearance isn't entirely fantastical.
Setna has a slightly higher attack than other priests, and he can carry relics, also unlike ordinary priests (without certain upgrades).