Quote Originally Posted by archon_huskie View Post
That leaves the question, "Why hasn't Good taken over yet?
I would recommend as inspiration the classic Star Trek episode "The Enemy Within", where a transporter malfunction splits Kirk into a "good" Kirk and an "evil" Kirk. The "good" side was too compassionate to make a decision, the "evil" lacked all inhibitions. In your setting that could be why the planes never go to war: the good planes lack the desire to go to war, and the evil ones are too busy fighting amongst themselves to think that far ahead, and even if they did they could not trust their own troops not to mutiny.

Blizzard's Diablo game cosmology did have a war like this, but the battlefield was the mortal plane. Apparently it was the crossroads linking Heaven and Hell, so maybe in your setting it could be the same, that the mortal plane is the only Interzone where both sides connect: no skipping over conquering the mortal plane first.