"Mark Of The Devil" came out in 1969, and was billed as "Positively The Most Horrifying Movie Ever Made," and looking at the time of its release, I could agree. "Night Of The Living Dead" generally freaked people out in 1968, but the recently deceased getting back up, and cannibalizing the living really does stretch credibility, where this film focuses on the cavalier attitude of Witchfinders in 1700 Austria.
People were superstitious at the time, and doing these awful things to people, and calling it "The Lord's Work," really did happen. The mere accusation of Sorcery was enough to get an indictment, and corruption of the Church has always been there; if you're accused, you have lost the battle.
Revulsion is the real star of this film, and watching these people doing these ghastly things to people, all in a days work, with God on their side, makes it excruciating to watch. One case in particular, has this LOVELY young woman on trial for consorting with the Devil; the truth? She was living with some nuns, and the Bishop raped her. The baby was seen as Satan's spawn, and the politics of the church wouldn't allow the truth to come out. She goes so far as to give a false confession, one she thought they wanted, and from there, it only got worse for her. Watching her ordeal made me physically uncomfortable; I had to keep reminding myself that she was just an actress, and this was a only film stage. But they really did this to people; that's what is so horrifying. THEY ACTUALLY DID THIS TO PEOPLE! WITH CHURCH APPROVAL! ("...doing the Lord's work is never easy...")
This is an exploitation film, but one with a story-line, albeit a tragic one, and thank God the witch trials don't happen now.