One word: Necronomicon. This tome presents heavily in Lovecraftian and Evil Dead lore. It's necessary if one wants to summon demons, Deadites, and who knows what else. If Evil Dead isn't directly Lovecraftian, it's inspired by it heavily enough that it might as well be the same universe.

It's possible that the force that chases people could be eldritch in nature or origin, because when it catches it's prey, it turns them into Deadites. This power is usually reserved for beings more powerful than demons.