Ironically, Terry Brooks is a Lovecraft kinda guy
By the way, Horrors don't just live behind the material plane, as stated by Jack Trowell. They actually live directly behind your monitor and sneak in through your computer via paths of electro-magnetism to infect the world of Dom3. When a Horror grows strong enough from feeding on little computer people, it spontaneously mutates into a Gamer, which is where the rest of us come from.
Mwuahahahahahaaa!!!!!