Religious Horror

A subgenre of Horror that relies on presenting the motifs of a real-life religion as fact within the story's universe. Since this is mainly a Western subgenre, that religion is Christianity (well, the only denomination that Hollywood knows of, at least).

Satan is the Big Bad in a typical Religious Horror story, although he's rarely shown. He is mediated through a human vessel, such as a Creepy Child or a degenerate rock musician. The protagonists are usually innocent people trying to live ordinary lives, not sensing anything wrong until their daughter or son starts speaking in someone else's voice, using foul languages she or he never studied, spewing Finnish pea soup, and/or chanting Satanic praises. Members of the clergy (most likely the Catholic variety; in this case it is justified by the fact that the Catholic church, of all the few that employ exorcism, is the most noted, although it does so very rarely) intervene eventually, with varying degrees of success. If there are human villains, they're evil cultists who facilitate Satan's activity on Earth (or, rarely, the Puritans of Salem, Massachusetts, if the author is less favorable toward organized religion in general). A variation is a woman giving birth to Satan's child. This type of horror is often written just to cash in on the popularity of The Exorcist.

 Occasionally, the story revolves around a Religion of Evil that has nothing to do with Satan, which may or may not replace him with an Expy in the form of a God of Evil. These tend to be more creative than the Christianity-based novels, but not necessarily more bizarre, as you'll see.