Spoilers - Question about Illidan novel

I have numerous questions...but one thing I'm having trouble figuring out. For the majority of the novel the portal to Azeroth is closed. Where did all of these elves come from to become Demon Hunters? I know a force of Blood Elves came through, and I know that the Sentinals are there. But where did the Night Elves come from that eventually became Demon Hunters?