The Damned is a slow burn, psychological thriller with a few moments of horror/gore. The tone is ominous and tense for the duration of the movie and you often feel something awful is about to happen which doesn't always occur. Music and sound during scenes cutting from one to the next are done very well to increase the feeling of foreboding and dread. If you've seen Haunting of Hill House on Netflix, it's along those lines as far as the level of horror. There is a lot to like about the film - cinematography, costumes, music, scenery, etc. The performances from the actors is also believable and compelling.
The "twist" ending is going to be what makes/breaks the film for the audience. Personally, I think if that final moment wasn't there, it would still be a satisfying ending to a horror film. Not trying to give away spoilers - but will add that the final sequence is one that makes the audience think and re-evaluate the events in the movie which I think is fun! If it angers you, then forget that happened and just acknowledge that it was a great scary movie. The reveal sequence is very abrupt and then the movie just ends which is totally intentional. You're left to ponder and draw your own conclusions. My husband and I had a lively conversation about what the ending meant for the entirety of the film on the drive home and isn't that what good psychological/mystery movies are for?
Overall, this was a refreshing "horror" film which wasn't over the top with gore (which I grow tired of). It was more classically spooky with slow build ups, figures in shadows, and characters that are absolutely terrified of the unknown. The artistry of the film deserves recognition even if you're left disgruntled by the ending.