The Deliver Us From Evil film, which is based on real life exorcisms, made for some of the most "disturbing" moments in the director's life as he watched some real life footage from an NY demonologist.

Scott Derrickson based his film on former cop turned demonologist Ralph Sarchie's many experiences with evil. He had previously directed The Exorcism of Emily Rose, but had a harder time with this film in particular way as he viewed many of Sarchie's personal footage.

"I saw a lot, I heard a lot and read a lot of cases in a very concentrated period of time back then. I think it was a little bit of an overload. It was very oppressive," Derrickson said to the Blaze, "Of all the things I've done "¦ it was that window of time that was the most disturbing time for me in my creative work."

The director showed some of the videos to actor Eric Bana, who plays Sarchie in the movie, and Bana said he was unable to sleep. It was at this time that Derrickson said his Christianity became stronger.

"When I went into the whole process of researching all of this and looking at all of this I made a conscious choice not to be thinking about it philosophically or theologically, but to look at it a bit more skeptically," he said adding, "What does this really look like? How credible does this seem? And I was genuinely surprised at the power of the testimonials of the videos and the documentation of credible cases."

Before he spent time researching he was not a believer in possession and demonic entities, but it became evident to him that it was indeed real and a serious problem. He feels that not all cases are completely the devil's blame; he would be hard pressed to go against the validity of it.

"I think you have to be unreasonable or have a dogma against anything supernatural to dismiss all of it outright. It certainly had a deepening effect on me in my recognition of these dark mysteries of the world," he said.

Derrickson wanted to capture this skepticism and struggle in the movie as the fictional Sarchie learned to believe in the supernatural and let faith guide his steps.

Watch Sarchie talk about the film below: