Something about it gives a sad atmosphere. I cannot say what it is, it's just there. I would guess that it is the guitar panned to the right ear. That indicates very good attention to detail, since you can barely hear it. I actually almost missed it.
Speaking about the guitars, you didn't use a that many major chords(or any?) up until 3:30, which I found was a good way to change the pace and mood. Suddenly sorrow is replaces by hope and strength. I like how the music follows along with the text or "backstory" also (even though I had a hard time reading it).
No instrument sounds louder than they have to, except the guitar panned to the right ear and the drums at the very end, if I should be picky. Unfortunately the song just cuts off att the last 5 seconds, which I hate when song do that in general. I don't know if I am a minority but I find it hard to listen to this because of the theme. I guess I get reminded of disturbing images :/