Here's a really excellent documentary series on history and folk horror:
Part 1: In this first part of a series of videos, we explore the history and folklore which inspired the Folk Horror genre in film and literature.
Part 2: In the second part of this series we investigate a book which is purported to be a religious text from a witch-cult in Italy; discover how pre-Christian festivals influenced folk horror; and find out why a murder in rural England inspired one of the first folk horror films.
Part 3: In the last part of this series on folk horror we will look at an influential study of folklore from the late 1800's which inspired many of the most popular folk horror stories, and finish by investigating the modern context which gave rise to the common themes of the folk horror genre.