Just like people, the gods had roles and responsibilities, jobs in the cosmos that only they could perform, as well as limitations. The gods of ancient Egypt were not omniscient and not omnipotent, but they could manifest themselves in different forms simultaneously, allowing them to remain in the sky or the afterlife realm of the Duat, while sending their bau to appear on earth.
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A god’s responsibility was unique, a cosmic role in the created world that no other deity could perform. Nut ensured the sky continued to exist. Shu’s force kept the sky and ground separate. Hapy governed the inundation’s yearly occurrence. Osiris enabled new life to spring from death – universal regeneration. The god Min ensured fertility. Because each god’s role was unique, if a god wished to perofrm another god’s function, the two had to ‘inhabit’ one another – a process called ‘syncretization’ by Egyptologists, and described as the gods ‘resting’ in on another by the ancient Egyptians. Gods were not all-powerful, and thus needed to the ‘force’ provided by another god’s responsibility to perform certain functions. So, for the god Amun to perform a fertility role, he and Min – god of fertility – inhabited one another temporarily to become Amun-Min, a new god who was at once both. Similarly, Amun, who embodied invisible and hidden power, might join Re – visible power – to form the all-powerful Amun-Re, the totality of visible and invisible power, the ‘king of the gods.’ In the middle of the night, the dying sun god joined with Osiris, to be empowered by his regenerative energy. The two gods then separated again, allowing the regenerated sun god to continue on his way into the dawn sky.
pp 111 – 113, The Egyptian Myths by Garry J Shaw (via satsekhem)