The first movie in all Spanish's cinema history made without Spanish government subsidies.
The plot of the movie is inspired in the H.P. Lovecraft's universe, mixing some ideas created by the Rhode Island's writer.
In the movie appears some real historical characters: Belle Gunness, Bram Stoker and Aleister Crowley. Belle Gunness was one of the sadly well-known serial killers in all history, Bram Stoker was author of "Dracula" and others novel horror books, and Aleister Crowley was an expert in the occult and he is considered one of the most famous black wizards.
Paul Naschy talked with José Luis Alemán to include Christopher Lee in the cast, but Lee turn down in the movie due others works he was doing when the movie was filming. Naschy is considered "The Spanish Christopher Lee".