Satan’s Slave falls into the category of cult films—a horror movie geared toward those interested in European-made, low-budget movies centered on occult themes. The story involves a young woman, portrayed by Candace Glendenning, who becomes entangled with a devil-worshipping group led by her uncle, Alexander Yorke, played by Michael Gough. The film uses standard elements common to this genre: nudity, violence, and blood, along with some memorable costumes—those goat head masks are something else! However, the entire thing feels excessively silly and the performances reflect that. While the violence is unsettling and there’s a degree of shock value, including a scene depicting attempted rape that would likely have made censors uncomfortable back then, the stretches of dialogue which form much of the movie's substance, are almost soporific. Director Norman J. Warren relies too heavily on horror clichés, and the overly bright and garish style becomes tiresome around the halfway mark; thankfully, Les Young’s striking color photography is a definite highlight. There’s certainly an audience for this kind of film, which explains its cult following, but it's something you have to be in the mood for—it won’t appeal to every horror fan. 4/10

Source on TMDB