The Devil Inside Her (1977)

A mind-blowing, demon-infested tale of incestuous mayhem! Zebedy Colt plays a puritanistic farmer who rules over his family with an iron hand. He sadistically punishes his daughters, attempting to repress their sexual urges. The daughter's response is a revengeful pact with Satan. The huge cocked devil possesses the entire family. Identities shift and transform randomly. The mother, father and daughters fuck one another savagely.