Blue Spoiler Alert: The ending is fucking retarded. It would have been better if the kid had been mauled by a werewolf. This is an example of Chekov's Gun. They could have removed the fucking shadow man and the ending would be exactly as satisfying. Why spend so much time telling us about this kid's crazy otherworldly roommate if the guy doesn't figure into the ending? Why does he so carefully avoid saying that he will not harm this child specifically?
And why does he still live under this kid's bed even after the kid decides to be a bossy, dickish roommate?