So, _Antrum_ is a found-footage horror movie. Think _The Blair Witch Project_, only Satanic.
There are really two layers to the film: 1. The documentary intro/outro, that prime you for what you are going to watch. 2. The movie proper. The first layer does a great job of setting an eerie tone, while the movie itself feels like a weird art film from the 1970s. Though I think the documentary pieces do a great job of filling in the blanks, I am curious to know what this would have been like as simply _Antrum_, and not found footage.
Speaking of, let's talk about the movie itself. It's very simple: a young boy's dog dies. His big sister takes his into the woods, where they are going to dig a hole to Hell, in order to rescue the soul of his dog. They happen upon two homicidal maniacs. The end.
By itself, that sounds boring, however the movie does a great job of maintaining tension - mostly with music and creepy visuals.
The aforementioned _Blair Witch Project_ is an easy comparison, although, I'd relate this more to _Yellow Brick Road_.
If you can wrap your head around Satanic, arthouse, cosmic horror, you'll have a good idea of what to expect.
Overall, I thought this was quite good. Truly unique. Very simple, yet effective.