Meg Tilly was incredibly uncomfortable in the actual mausoleum. Her reactions to her surroundings were often genuine. During the scenes where she was hysterical, she actually did throw herself into hysterics and it took her awhile after each take to calm herself down.
Martin Nosseck passed away two days after filming his scenes. When his family came home from the funeral, his check had come in the mail itemized under the film's original title "Rest in Peace."
Adam West was not the first choice for Allan, but when the casting director told Tom McLoughlin that no one would hire West because he was so recognizable as Batman, he felt sympathy for his fellow actor and told them to put him in the movie.
Actual skeletons imported from India were used for some of the corpses.
Tom McLoughlin and Michael Hawes had little control over the final product and it was edited without their consent. When they saw a sneak preview they were shocked because their ending had been cut out. In a desperate plea, they begged the producers to let them shoot one final shot. The actors, crew, and special effects team agreed to come back for free to film the final shot in Tom McLouglin's garage.