Cool man
You really nailed down the whole Halo-esque ambients there. I can just imagine, walking down a dark corridor, scared shitless, because I don't know when I'm going to get attacked.
The beginning, was probably the worst part of the song. The piano chords were way off tune with the strings.
The next ambients part of the song was done extremely well. You successfully created a great atmosphere, very much like halo.
When the second halo melody came in, it gave it a very nice ending.
Overall great piece, except for the begining piano chords.
-SineRider