Ra is the living Neter who descends into death to become Osiris (Aus-RA means the power of RA in Egyptian & you'll find the name AUSAR too), the Neter of the dead
The creation is continuous, like a flow of life progressing towards death. But from death is born a new Ra, germinating new life.
Ra is the cosmic principle of the energy that evolves towards death and Osiris (Aus-RA) represents