Very nice and atmospheric! My only comments are:
It sounds great, and I'd love to hear the final version of the track!
- The percussion, particularly near the beginning (around 0:25), seems like it's in a different acoustic space than the other instruments -- much further to the front. I'm afraid my ears are trained more to orchestration and form and less to effects, so I can't tell for sure, but it sounds like there's much less reverb on the drums than the other instruments.
- The string ostinato is very effective at first (around 0:50), but it gets a bit old after two or three minutes. Try switching it out in the more climactic parts with French horns, and put the strings on the melody instead. Or you could leave the strings in but transpose them down an octave for a subtler effect. I realize that transitions in background music need to be smoother than those in foreground music (like credits), but I think it could still use a bit more variation.
- It seems like the same two four-bar chord progressions are repeated throughout the piece. You might consider inserting a slightly different section in the middle somewhere, like a bridge, before the main theme comes back again.
It sounds great, and I'd love to hear the final version of the track!