Sia as a god personifies the perceptive mind. He was created from blood dripping from the phallus of Re, the sun god. In the Old Kingdom, Sia is visualized at the right side of Re and responsible for carrying the sacred papyrus whose contents embody intellectual achievement. On the walls and ceilings of tombs in the Valley of the Kings, Sia travels in the boat of the sun god. He was the spokesman of the sun god in the Books of the Sky (Heavens) and the herald who stands at the bow of the solar bark in the Book of Gates.
Sia, who was part of a complementary pair consisting of Sia and Hu, is probably equated with the intellectual energies of the heart of Ptah in the Memphite theology, resulting in the creative command of Ptah's tongue. However, it appears that Sia never benefited from a cult in his honor.