As a long time player of D2, but having never gotten into the lore much, I read through this thread and found it absolutely interesting. I have a question now, naturally.
"The Nephalem, being born of Angel and Demon, were found to be quite powerful. Lilith planned to use their power to build an army, but Inarius fought against her and used the Worldstone to nerf the human's powers, so that each successive generation became less and less powerful. He wanted control over them, not anyone else."
(I can't use the bbcode yet)
If this is the case can one assume that with the destruction of The Worldstone that the descendants of the Nephalem will become uninhibited towards their full potential? Could humans as a race become a (or even THE) dominant force now that The Worldstone can no longer "nerf" the power that they could have theoretically had if it hadn't been brought into existence? Perhaps with their new found powers, and the inherent instability of humans, they themselves could become the evil they've been trying so hard to defend against.
I just had this idea in my head while I read through this thread so I just had to say something.
Oh, and from what I've read just based on this thread it sounds to me like The Black Abyss is a spawning pool for demons, almost like a primordial ooze from which they spill or are created, as where The Void is an alternate dimension from which there is no escape from the "inside" of it, however it is highly plausible that (especially in regards to the portals leading to Lilith, etc) a gateway to The Void can be opened from the human plain, as well as other plains not only to banish things into The Void, but return them out of The Void as well. You can also assume that each individual, demon, human, anything, has their own specific "The Void" so that they are always in solitary unless someone from the human (or other) world opens a gate to their specific "The Void" whether to slay them, release them. Whatever they wish, however it would certainly take a considerably powerful magic user to open such a gate, or at least powerful magic relics (Key's of [whatever], Organs)