Religion has a huge place in horror, aside from the fact that it is a horror that millions upon millions of naive, weak minded sheep believe. But forget about that, what about movie likes The Exorcist, Rosemary's Baby, The Devils Rain, The Brotherhood Of Satan?!?! Religious horror has become an enormous subgenre! There was a two part special in Fangoria magazine not too long ago called Devil Movies: Celebrating 25 Years Of Satanic Cinema. It was a great article, I suggest you read it, just for the fun fact that you might find some horror gems in there ya never heard of. I know I did!