What is the source of evil? Many think it comes from within humans, even the church teaches that, but "Prince of Darkness" presents the terrifying idea that we are not in control of ourselves and all of the laws of science that we tell ourselves are lies invented to hide the scary truth that maybe there is evil out there that we can't understand, that is beyond our control. Of course, we hide from it for as long as we possibly can, focusing on petty romances and telling dumb jokes (*cough* Walter *cough*). We depict Satan and evil in TV, cartoons (like the "Tom and Jerry" episode shown in the film), or corny horror movies, like "Prince of Darkness" itself, so we can tell ourselves it's not real. We might try to stop it, such as the unsettling "not a dream" broadcast, or the various attempts by the priest to kill the thing that Kelly becomes, or finally Catherine's final sacrifice, but ultimately, we see with the ending, all of these attempts are futile. They are at most a slight delay of the inevitable take over of this ultimate evil.
Yes, the acting is bad. Yes, the film is cheesy, despite some genuinely unsettling moments and images (namely, the very end, the aforementioned broadcast, worms piled onto windows, a pigeon crucified, an unusually friendly woman holding a cup of writhing maggots, and the moment where the man suddenly decomposed in the pitch black darknees outside, and the beetles that suddenly appear at his feet and climb around him, not to mention that classic Carpenter score). But I think that even this cheesiness fits with the themes of the film in a way.
Yes, the acting is bad. Yes, the film is cheesy, despite some genuinely unsettling moments and images (namely, the very end, the aforementioned broadcast, worms piled onto windows, a pigeon crucified, an unusually friendly woman holding a cup of writhing maggots, and the moment where the man suddenly decomposed in the pitch black darknees outside, and the beetles that suddenly appear at his feet and climb around him, not to mention that classic Carpenter score). But I think that even this cheesiness fits with the themes of the film in a way.