I really think they're making this movie out of the hype this character got back in conjuring 2. The story line was mehh. At first, I thought that Valak is an actual nun who have sinned and became the most dark spirit and terrorizing people but no. Valak is not a nun! That alone got me really upset and this movie only really on the jump-scares which work like always.
They should've make a story about a nun who is obsess with serving the God but eventually felt sorry for Lucifer and start worshiping him instead and made a sacrifice to be the vessel for Lucifer to enter our world. Because she is a nun and people wouldn't suspect anything until one day her fellow sisters found out who she had been worshiping behind closed door. I think it is much more better no?
I'll give this movie 2.5/5 stars for the story line.
P/S: The humor did some justice to the movie.