The thing that spoiled the twist to me was..
When she started seeing the faces at the farm house. When at the Shrine, i was thinking:"Oh dear lord, don't let this be any generic monster cult movie", and at the farm house, i realized what was happening.
I wish they would have left the monster faces off completely, it would have been a twist, at least for me. And somehow hinted that something was after Carmen when she went into that room at the farmhouse, then grow the suspense before letting her attack Marcus.
This was a good movie imo, could have been much better one. We still enjoyed it with my gf though.