Special Effects man Bob Keen had to go back and shoot more scenes after initial test screenings of the film found it too light.
Philip Yordan originally wrote this script in the 70s after the box office successes of films like The Exorcist (1973) and The Omen (1976). Director Vila found the script years later in Yordan's office while they were working on something else, liked it and asked if he could use it.
Director Camilo Vila proclaimed that this was not a horror film during its initial release despite the fact that the film was about literal demons from hell.
Lari White's debut.