Was the angel that possessed the wendigo Tyrael? I assume it was since he's the only angel to have meddled in mortal affairs thus far, but obviously it is never confirmed one way or the other.
Also, was Karybdus the Necromancer hero from Diablo II? The book touches on his past accomplishments, but does not specify defeating the Lords of Hell as "Firefly" does with Isendra the Zann Esu. As well, the Necromancer's Log found in The Stinging Winds points out that his mentor is the necromancer hero from Diablo II, however does not specify if he is alive or dead. If he is alive, then obviously Karybdus is out of the equation. Otherwise, based on the timeline of The Moon of the Spider and the estimated age of Mehtan the Necromancer, I don't see why it's not possible. I am leaning towards that Karybdus is not the Necromancer from Diablo II, but I am not sure yet.