2 QUICK QUESTIONS:
1)What was up with the large guy with the brief-case at the beginning? Was this ever really revealed?
2)The lead female demon said late in the film "we know you have a helper--but we don't know who--where is he" blah blah. ...Uh...shouldn't they know? First of all, given his eventual backstory, I would have thought he would be a prime suspect in their eyes. PLUS: the first time we see him he is attacked by a demon and pulled down a dark passage. ...The only way I can see this not being a plot-hole is if he turned around and killed the demon dragging him.
The art of losing isn't hard to master.