Everything is set up for a nasty twist. Even moreso because we don't expect any story at all. They soothed us into complacency by both the confusion of the original, and by having us face the horror of the Hive in all of its "ultimate evil" glory. Now, we get to face the warped mirror of the Fallen. They could drive that knife deep, twist the heck the heck out of it, and there's no way we could be emotionally prepared for it. It could be epic. Ach. Who am I kidding?