I know this is speculation, but what if diablo transfered himself to adria and send a corrupted aiden away to draw atention to him and hide.
So this corrupted aiden, under diablo's orders frees the other primes to have them defeated by the heroes. in hell we kill aiden, whio is possesed by another demon and 20 years later he comes back in Adria to fullfill his plans at last.
An Adriablo could be the reason diablo looks feminine in the game and having possesed a witch could imcrease its power making him an even more formidable opponent. (and remenber that with this theory we never fought diablo in d2)
EDIT: and death spreading its wings could be a references to the dragon who taugh dthe necromancers.
So this corrupted aiden, under diablo's orders frees the other primes to have them defeated by the heroes. in hell we kill aiden, whio is possesed by another demon and 20 years later he comes back in Adria to fullfill his plans at last.
An Adriablo could be the reason diablo looks feminine in the game and having possesed a witch could imcrease its power making him an even more formidable opponent. (and remenber that with this theory we never fought diablo in d2)
EDIT: and death spreading its wings could be a references to the dragon who taugh dthe necromancers.
What i doubt is diablo posessing an angel. It could happen but it is not explicitly written in the prophecy like the angels' fates.