A hell of a good job!
The single fact that this takes place in a subway, the claustrophobic streets of a deserted city and a surreal labyrinthine movie theater for most of the running time makes Demons unique and memorable. The “demons” are somewhat quick and growling zombies with scarier make-up and a permanent evil grin. They’re filmed with intensity and often under a red light. They are spine-chilling.
They’re relentless killers and they provide the appropriate gore. They compensate for sometimes absent performances from colorful characters that should be more exposed. Despite our detachment to the protagonists and the little dialogue they’re given, we can see through their assigned stereotypes fine and then fill in the blanks. The demons matter and they’re given all the backstory we need.
Indeed, the script isn't as minimalist as it appears at first glance. The infestation is caused by contaminated promotional material and a reel that summons evil when played. The introduction and the ending are ambiguous and far-fetched but they remind us of how deep this mythos is. Demons piggy backs on a religious concept by name only. The creatures, here, are like nothing we've seen before!