Evil is the absence of good. Hence it would follow that it non-exists separately from all creation. Yet wishes to infiltrate it. But will inevitably fall short of its goal because it is a lie.
I would suggest that the opposite is true: good is the absence of evil. Evil is active whereas good can be passive - e.g it's "good" not to meddle in other people's affairs. So a creator of evil is necessary whereas a creator of good may not be.
Only in my second statement, which merely points out that polytheism provides for much more variety in the behaviour of divine beings. Not all gods are good, nor are all gods always good-acting. That's far too simplistic. In the first statement--which you have still not addressed--I'm talking about your monotheistic god. The god of Augustine, Thomas Aquinas, of the Christian theologians. Your god, on whom you are placing limits, which runs counter to its very concept.
