I have a few questions:
1. At the beginning I seem to remember a child having been found dead, killed by the monsters from outside. If the monsters are really the elders, why would they kill their own just to make a point? Isn't that the very sort of crime they're trying to leave? And if I'm wrong about what happens, how do monsters scare villagers other than having stories told about them? Every now and then I'm sure some villagers must get curious and want to actually see bad things done by the monsters to realize they're truly bad. But if bad things are done, it's a crime - a sort of catch 22.
A possible alternative is that when someone dies of a natural cause, the elders blame it somehow on the monsters. The problem with that is those close to the ones who died of natural causes will sometimes realize what's going on and the secret is in danger of being spread.
2. I have trouble understanding Noah's actions. Was he trying to kill Ivy at the end? Just scare her? If he was trying to kill her, why didn't he do it before she left town - it would have been easier. If that is explained by him being mentally handicapped then how do you explain the amount of planning that went into having him find the elders' shed, put on the costume, and stalk Ivy for some time in the woods. Also, why did he put the monster's costume on at all? Ivy can't see him, and she would be the only one outside. It looks like something that does not flow with a character's motivations but is there just for the movie's scaring purposes.
I think that's all - for now
ETA: One more thing, what was the deal with him falling? Did he die? Was that a real trap or just a ditch?