From The Grindhouse Cinema Database
- Out of circulation for years after Warner Bros. sued American International claiming it was a rip off of their film The Exorcist (1973).
- Filmed in Louisville, Kentucky, the production was temporarily halted when a series of tornadoes ripped through Louisville on 4 April 1974. Carol Speed recalled taking refuge with Juanita Moore in the lobby of a hotel that had no tornado shelter. They weathered the storm wrapped in blankets to protect them in case one of the large glass windows exploded.
- In addition to the devastating tornadoes that struck during filming, there were more instances of bad luck on the set. Actor Terry Carter broke his ribs filming one scene, and whenever Carol Speed would appear on the set dressed as the demon, the generators would fail.
- The song that Abby sings in church, "Is Your Soul A Witness?", was written and performed by the actress herself, Carol Speed.