Devil’s Nightmare (1971)

aka’s: La Plus Longue Nuit Du Diable/
Au Service Du Diable/La Nuit Des Pétrifiés/Succubus/The Devil Walks At Midnight/The Devil’s Longest Night

Six of seven tourists staying in an east European castle overnight are victims of a servant of the Devil, played by Erika Blanc. Also stars Jean Servais and Daniel Emilfork.