The Sun and Moon Entities in the Soul Seater floating in the Sky Aren't the real Sun and Moon but are in reality Artificial Entities AKA Golems Created by the Gods Apollo and Artemis respectively.

These two Creatures were Created Thousands of years ago to Act as Guardians of the day and the Night And they specifically fly and Rotate over Death's school in Nevada because That is where Death Lies and is bound to and with Asura Underneath Him They Look over them to make sure neither of them ever Poses A Threat to the Mortal Race.