This review will have some serious spoilers, so if you don't want that, stop reading. If you haven't watched this film yet, and this is the first time you hear of it, for the love of everything you hold dear, watch it as soon as you can and avoid trailers and reviews like the plague. The less you know and the less you expect, the better it will be.
Best demon-themed horror film I've seen since "The Possession"! I had unusually high expectations since I thought this would be something unique, so I honestly expected this to be a huge let-down, but thankfully it was literally the exact opposite: unlike just about every other similar film, it was unpredictable and didn't rely too much on jump scares. Although the fact that it involved demonic possession came as a surprise to me (I mean, I expected this to be some kind of fucked up psychological shit), and I hope the writers/director intended it to be an early plot twist of sorts, since if that was their intention and they pulled it off this well (that in the beginning, it could've gone anywhere), that only makes this feel like an even more amazing film.
I'm pretty sure I've already mentioned in some other review that I practically never watch trailers, so of course I've gotten used to sitting through hours of total shit and my standards aren't all that high, but there's no bias in the statement that this is one of those films that will make it into thousands of people's top 10 lists this year.
...but it's not perfect. There are some half-assedly covered plot holes and at times the effects are a bit over the top in terms of comparative realism within the film itself, but they're far from ruining the atmosphere. One thing, though, that half of the plot relies on, seems to have been completely forgotten by everyone involved in the making of the film: the levitation/teleportation/whatever. Like, that's the first genuine mindfuck moment, yet it's the only one of its kind. Why does she suddenly not do it anymore, and what the fuck was the point of doing it in the first place?
Anyway, that's nitpicking. The ending was absolutely terrifying, and this is the first film I've ever seen pull off a demonic mouth-stretch effect that actually works and looks creepy as hell rather than laughable. I'm gonna give this 99/100. Try to beat that.