Satan's Slave

Satan's Slave is a 1976 British supernatural horror film directed by Norman J. Warren. It was written by David McGillivray and stars Candace Glendenning, Michael Gough, Martin Potter, and Barbara Kellerman. Its plot follows a young woman who, after surviving a car accident, stays on the country estate of her uncle and cousin, unaware they are both necromancers who intend to sacrifice her to resurrect the spirit of a supernaturally gifted ancestor.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.