Syncretism

Religious syncretism is the blending of two or more religious belief systems into a new system, or the incorporation into a religious tradition of beliefs from unrelated traditions. This can occur for many reasons, and the latter scenario happens quite commonly in areas where multiple religious traditions exist in proximity and function actively in a culture, or when a culture is conquered, and the conquerors bring their religious beliefs with them, but do not succeed in entirely eradicating the old beliefs or (especially) practices.