The Reincarnation of Isabel (1973)

In the late-1300s, the beautiful and innocent Isabella is tortured and burned at the stake for supposed witchcraft, in front of her lover who swears revenge. Several hundred years later, the well-off Jack Nelson and his niece, Laureen, celebrate the latter's engagement at their newly-acquired and fully renovated castle, unbeknownst to them that in the château's dank cellar, evil occultists participate in ancient black magic rites, sacrificing youthful virgins. What are their intentions? Is Laureen next in line?