The source of:
-Angels vs. Devils (The word ‘devil’ itself derives from Zoroastrian mythology: ‘Dev’, ‘Daeva’)
-God vs. Satan
-Heaven and Hell
-Free will in humans that makes us participants in a battle between good and evil on earth.
-The coming of a savior.
Basically, the philosophy, world view we see in games like Diablo is a very distinctly Zoroastrian way of thinking that passed down to Abrahamic faiths.