Note that all things proceed from the monotheistic God. Later, the developing character of Satan or the devil allowed us to personify evil and project it outside ourselves. All cultures have myths about the origins of Good and Evil. In the West, the monotheistic cultures struggle with the problem of where evil comes from if everything comes from god. In the east, where polytheism prevails, good and evil can be divided between different deities, although as we have already seen, there too good and evil sometimes emanate from the same source.
Some cultures create a very strong duality of good and evil.
Sometimes the good god battles the bad god. Sometimes it is an evil goddess in conflict with her brother, the good god. Sometimes creation itself is seen as a battle between the forces of Good and Evil. Sometimes evil is introduced by a trickster, who lacks a moral consciousness. Modern psychoanalysis tells us that all of these myths are ways of splitting off parts of ourselves and distancing ourselves from evil.