This doesn't come up much in Reformed circles, and understandably. The Bible alludes to this kind of stuff about once. It is not high up on the list of importance. But it is also irreverent to God to say "it's not important" either. The passage One can assume that an angelic being is conversing with Daniel. This being mentions a struggle with the prince of Persia, which could be a mortal figure but I believe the context suggests that it, too, is an angelic spirit, if a dark one. Without endorsing Frank Perretti's material, what would territorial spirits mean for Christian spiritual warfare today?