Terror, Sex and Witchcraft (1968)

Vicky loves Ricardo, but Ricardo loves Barbara. So, Vicky visits a gypsy witch who convinces her she must make a pact with Satan in order to cast an effective love spell on Ricardo. After Vicky gives her body and soul to the Dark One, she engages with Ricardo in a passionate night of lovemaking that is cut short by Satan, who, sensing that Ricardo has not completely fallen under the spell, orders Vicky to kill him. Following Ricardo's death, his brother Carlos is haunted by nightmares of the dead sibling, who appears and takes possession of Carlos in order to get his revenge...