Euro-sleaze from the 70's doesn't get any more prototypic than "Feast of Satan", with its lurid atmosphere, scantily clad women running through the woods all petrified, horrible dunning, sinister organ music overload, shamelessly borrowed influences of American landmark horror movies and the thinnest possible storyline imaginable. When her sister Maria is repatriated from a vacation resort in a severe state of mental shock, with the characteristics of being petrified still noticeable on her face, Hilda Salas travels to the area to investigate what happened. She gradually becomes entangled in a world of occult mystery. The more Hilda gets acquainted with the local high society, and particularly the hunky Dr. Tills Nescu, the more her life is endangered. As said, "Feast of Satan" is pretty standard guff and thus predictable, derivative and largely boring. The film is surprisingly – and unfortunately – very sparing with nudity and gore, so you simply have no choice but to pay attention to the decrepit plot. Due to the complete lack of action and suspense, the film seems to go on forever without revealing any clues regarding the denouement. That is especially annoying since the title pretty much openly gives away what will happen at the end: one giant satanic orgy, of course! Though I have to admit the final couple of twists and red herrings, as well as the climax sequences, uplift the quality level of the movie in general.
Here's a tip in case you really get too bored to be bothered with the actual film. Keep an eye open for the Dr. Tills Nescu's short-sized and mustached employee. He makes the highest amount of pointless cameo appearances I've ever counted. It's like he came for free with the camera!