This article explores some important parallels and differences between certain Eastern Christian and Islamic heterodox (Alevi/Kizilbash, Yezidi and Ahl-e Haqq) cosmogonies, which shared and developed old cosmogonic themes such as the ‘primal ocean’ and the ‘earth-diver’-demiurge, and co-existed during the Ottoman period. The investigation reveals that some of the Eastern Christian versions of these cosmogonies have retained their archaic forms, but in most of them the earth-diver is identified with the Devil, a movement towards cosmogonic and religious dualism that could have been effected by both heretical and popular Christian diabology. Conversely, despite the existing traits of dualist and earth-diver cosmogonies in Northern and Central Asian non-Islamic Turkic and related religious traditions, a comparative analysis as demonstrated in this article shows that the Alevi/Kizilbash, Ahl-e Haqq and Yezidi cosmogonies did not absorb or develop these dualist features but rather tried to neutralize them by reinterpreting them in a largely monotheistic framework.