The Endless (2017)
While not at the same level of greatness as "Mandy", "The Endless" shares some elements such as: drugs, a crazy pagan cult, and some kind of weird fantasy-scifi thing happening. Now, in relation to the paranormal mystery, there are some references to Lovecraft too. But overall, I thought the main core idea (or at least part of it) was kinda new, but I'm not entirely sure. Also, Callie Hernandez is co-starring in the movie.