The film had only one camera for the whole shooting.
Rocco Carduncho is loosely inspired by the archbishop Rouco Varela. The name given in the film is inspired both in Rouco Varela and Rocco Sifredi, but the surname is taken from Vicente Carduncho, an Italian painter based in Spain who painted the 54 canvas of the cloister of Chartreuse of El Paular. This monastery appears in the movie.
Famous dancer and performer Conchi Naranja refuse to appear in the movie because, as a budist, she is not allowed to make horror movies.
Shooting took place only for five weeks, with one spare week for the Holy Weekend.
Tristan B. was inspired by Tristanbraker, a real ghost buster who became famous during the nineties, just a decade after the foundation of HEPTA.