Word of warning though, if you are the type that needs all the questions answered in a movie, then you best pass on this one. Even after watching both of them there were still questions.
Where these movies excel, is with the uncanny cosmic horror. With Resolution, it's merely hinted at, but The Endless takes that idea, sets it on fire, and runs it down the road parading it like the Olympic torch.
Here's what worked with Resolution: the acting and strange goings-on work on a level that spoke to me. I like my horror weird, creepy, and head-scratchy for the most part, and this movie hits those marks. It was weird, in a good way, with some genuinely creepy moments.
Where it begins to fail (although after watching both movies, the failures are actually successes; however, I realize that someone shouldn't have to watch both movies to fully understand something...movies, like books, need to stand on their own two feet) is with the randomness of the weird things happening. It got to the point where I thought that perhaps the writers and directors just compiled as much weird shit as possible and ran with that idea without fully realizing where the destination would be. The ending is strange and left me with more questions than answers.
Now, let's circle over to The Endless. There is a scene in Resolution where the protagonist comes across members of a UFO death cult. It's a very short interaction, but one that has bigger impacts with The Endless. Two of the people he met in that interaction are the main protagonists in The Endless. They play as brothers who left the death cult. They receive a strange video of the other members welcoming them back, and long story short, they decide to go back for one day.
As I mentioned before, where Resolution left you with the idea of cosmic horror, The Endless solidifies it. There's something out in the woods (which isn't a spoiler) that the cultists are worshiping. When the lead cult member is asked by one of the of the brothers, he responds with this (paraphrasing here), "it's something different for everybody. If you want to know what it is, then go find out for yourself." I really liked that notion.
The movie also had a mix of moments. There were a couple of genuine comedic (albeit, dark comedy) moments that stuck out. I won't spoil it here, but one of my favorites was when they gave one of the characters a gun that had been requested. Mixed with that, were some terrifying moments...again, no spoilers, but the tent scene was particularly disturbing, especially when you realize what's going on, and what that character inside the tent is having to live through.
On a subtler level, there is an aspect of horror with seeing a difference in reality. The older brother realized that staying with the cult would mean their potential death, which is why he took his younger brother and left so long back. The younger brother only remembered the good things about the cult, and when faced with his not-so-great present quality of life, he wanted to go back. The movie was great with showing the conflict between these two and the decisions they must face as the story pushed forward.
There were a couple of plot holes and head shakes, but for the most part, The Endless was solid. The acting was good, the story was great, and the atmosphere was amazing. I found the ending somewhat ambiguous. I took it one way while my wife saw it differently. It kind of ties back into the quote of, it’s something different for everybody. It touched on all the key points of cosmic horror for me and left me wanting another movie by these two directors. Overall, a great addition to the cosmic horror movies out there, and I consider it a must see if you like horror movies that have a weirdness to them.