What a load of shit this one is. A couple of good ideas, a bunch of bad ones, and a whole lot of padding gets you this flimsy lark. From the trailer, I assumed they were ripping off Cigarette Burns, John Carpenter's first season episode of the "Masters Of Horror" series. I imagine they think they're getting around the comparison by mentioning both it and The Ring films during the faux documentary portion of the film that bookends the "lost" film, Antrum. They obviously got their inspiration from Cigarette Burns, but they didn't learn its most important lesson: no matter what you show, you can never make a "cursed" film look like something someone would actually believe is cursed. And, instead of even attempting that, they just filmed their own boring little short film and called it a "cursed movie". If Antrum had just been the film and had eschewed the lame documentary portion, it might have passed scrutiny as a somewhat symbolic indie film trying to pull off the feel of a lost film from a specific era, much like Beyond The Black Rainbow managed. I'd be more prone to believe that movie as a cursed film than what these filmmakers ended up with.
So, straight off, you're seeing the bar set far too high with the opening (and closing) documentary segments, explaining the nebulous history of the film, the death of those festival-runners who turned down the film, and the tragedies that befell screenings of the movie. When you follow this by seeing the boring, placid movie, it comes across as absurd. I can't think of any reason a festival-runner would turn down the film, except that it's kind of dull, but that's par for the course with a film festival. Especially if you're claiming the movie came out of the late 70s; in that case, the film could have easily been worthy of viewing during that time period. It goes to great lengths to point out the weirdness of the movie, which really isn't there. I don't think anyone would be scared by the pseudo-subliminal negative scratches and spliced in bits of torture footage (mostly implied, since the movie feels very PG-13). The crux is that a film that kills people or makes people go insane should feature visuals equally unsettling and strange. Not just gore, for that matter. The film did some good work with its dark silent-movie-style demon images, often superimposed slightly into the picture. Strange and incongruous visuals combined with something innocent might be good, but this movie-within-a-movie plays like a horror movie itself. In The Ring, they didn't end up watching clips of some arty foreign horror film on the cursed video tapes; instead, you get strange, metaphorical images and, even then, you're not scared as a viewer. You fully accept that the curse exists within the framework of the movie, but only a fool would paint themselves into the corner of saying the whole movie you're viewing is dangerous and could kill you. That's 1950s Barnumesque B-movie showmanship, but no one's going to walk out of that sort of movie impressed, no matter how much 70s grindhouse film grain you put on your digital video.
As for Antrum itself (or perhaps the sub-Antrum within Antrum), it's a supposedly Eastern European-made but obviously very Southern California-filmed movie of exceptionally short length but very minimal plot about a boy and his older sister who go to a local suicide forest to dig a literal hole to Hell. We find over the course of the movie that perhaps the boy was already infected with evil and, attacked by his beloved golden retriever, was forced to euthanize his pet. His mother tells him that his dog was bad and therefore didn't go to heaven, and he begins to obsess over his dog being in Hell instead, which his sister blames for his constant nightmares. (By the end of the film, we're led to believe that maybe that wasn't true and the nightmares had darker origins than a dead dog's misplaced soul.) His sister fakes a grimoire and rituals, telling her brother they're descending through the levels of hell as they dig a small hole next to their campsite. She plans to plant the dead dog's collar, a symbol to show her brother that they've saved the dog's soul from hell, nearby so that he can find it during their search and let go of his obsession. Instead, her brother starts to unravel and they come across the camp of strange foreign killers who cook their victims inside a metal statue of Baphomet; it's often stated in synopses that they're cannibals, but nothing in the movie really gives that impression. The kids wander around, trying to escape the area and somehow failing. The boy is completely lost in delusions about their descent into hell (Or is he? Dum dum duuuum!) and his sister also starts to crack under the strain. They're kidnapped by the potential cannibals, but manage to escape, the sister shooting both of them. The kids get separated, the sister ends up back at camp, beginning to see the demons her brother has been seeing, and the boy saves a dog from an animal trap, giving him his closure. He arrives back at their camp toting the animal trap and making as much creepy noise as possible and refusing to answer his sister's cries, while his sister huddles in their tent and points a gun at the opening, inevitably going to shoot her brother the moment he opens the flap.
As for the acting, the child is... as children are, kind of annoying. But he's believable, at least. His sister, played by the very pretty Nicole Tompkins, really gets the best of the movie and is the only one that really comes out of it looking good, mostly because she acts the hell out of what little they gave her. The rest of the actors who briefly appear have histrionic performances of varying calibers that mostly aren't worth mentioning.
I feel like there was possibly an idea that could have worked in here somewhere, but they didn't find it. Initially, I thought there was a rifle on the sister's pack and that perhaps the digging and ritual would lead to her shooting her own brother, the hole becoming his grave. That might have been more interesting than the very horror-cliche-standard running around and screaming that followed. There's odd imagery that works at times, but the tryhard film scratches, very lame and cliched spliced-in torture footage, weird distorted sounds and noises, and unnecessary mid-movie villains just make it seem like they really didn't know what they were doing or trying to go for. Shouldn't a cursed film feel more like something that manifested itself and is inscrutable, possibly maddening, to the human mind? Why would it feel like it was scripted, cast, filmed, and edited like every film ever? Maybe without the bad premise and the fucking shitty "The Deadliest Film Ever Made" tagline, it could have survived on its own merits, but that wasn't how they conceived the film. They wanted to explore the idea of a cursed film and a cursed film wasn't the movie they made. They should have just made the faux-retro metaphorical short film and called it a day.
It was dull enough that I stopped watching it, went to bed, and finished it the next day. It's shocking how little of interest makes it into the movie and the attempts to make it seem spooky made me audibly groan. As a film, it's boring and mediocre, but as a film with a larger, unsuccessfully grandiose concept and framing device, it's even less than that.