We can see from the example of Leviathan how the great ‘fish’ gradually split into its opposite, after having itself been the opposite of the highest God and hence his shadow, the embodiment of his evil side.
Jung argues that Leviathan exemplifies a psycho-mythological splitting process in which an original divine shadow bifurcates into a pair of opposed monsters, relocating God’s inner conflict onto an external cosmic drama.
, Aion: Researches into the Phenomenology of the Self, 1951thesis