El Retorno de Walpurgis (The Return of Walpurgis, also known as Curse of the Devil) is a 1973 Mexican-Spanish co-production horror film that is the seventh in a twelve-film series about the werewolf Count Waldemar Daninsky, played by Paul Naschy. This film ignored the events in all of the earlier Wolf Man films and began an entirely new origin for el Hombre Lobo, which is strange because the film's Spanish title The Return of Walpurgis seems to tie it in with Naschy's earlier 1970 film Walpurgis Night. The Wolf Man makeup was done by Fernando Florido. The film was shot in June 1973, and by September, it was already in theaters in Spain, as El Retorno de Walpurgis. It wasn't released theatrically in the U.S. however until 1976, as Curse of the Devil.

It was shown in Germany originally on August 7, 1974, as Night of the Diabolical Orgy, then was re-released on October 7, 1974, as Die Todeskralle des Grausamen Wolfes / Death Claws of the Cruel Wolves. Mexico released it as Night of the Killer, France as L'Empreinte de Dracula / The Mark of Dracula , and Belgium as Return of the Loup Garous.

This was the last film that Naschy worked on with director Carlos Aured. As soon as the film was completed, Aured became very cold toward Naschy and never again asked him to work with him. Naschy said in his autobiography that he never understood why Aured acted that way toward him, but he surmised that perhaps Aured thought Naschy was becoming too controlling on their collaborations, since Naschy was not only starring in the films, he was also involved in writing and casting them. (They reconciled their differences in 2007, but by then Aured was just months away from dying.).

This film was followed by Naschy's eighth Hombre Lobo film La Maldicion de la Bestia (1975).