Holy cow. My mind is blown. Everything from the title, to the director dying 5 days after submitting the final cut, to the location chosen to film the cult party. These links are a long read but a great explanation of the movie.
So many unbelievable things that I've come across in this group are confirmed by this movie. I saw someone mention it in a comment months ago and glad I finally came around to watching it. It was very strange in the beginning, but you have to remember you're not watching a regular movie, you're watching someone trying to show you what's going on without explicitly saying it. After reading the above articles I am just blown away.
For me always the scariest horror movie, because it seemed so real. The way the evil people just blend in and seem normal. The husband's ability to rationalize to get what he wants. Very scary.