I'm seriously starting to think that the Engineer we see in the trailer is actually one of the Prometheus crew, forceably mutated into one. Just look at the suit he's wearing--it looks a damned sight like the Prometheus crew suits, even with the cowl at the back--which, interestingly enough, seems to be part of the Engineer's neck, biomechanically fused. Methinks that's what our Mutant Space Zombie friend might be turning into--or maybe the Engineer activating the chair is actually Holloway, since we know he also gets hit with the acid/whatever as well. I remember reading a while back where someone hypothesized that the Jockeys themselves are long dead, and need human hosts to resurrect themselves. Hmmm.