The demonic entity attached to the app is pretty frightening in appearance and screams like a banshee every time it lunges for a victim; it also frequently poses as its former victims, but hideously deforming their bodies & faces.
Everytime a victim's countdown is coming close to the end, the film is very suspenseful as they try to escape it; their phones also frequently scream and make loud noises to warn the victim that death is coming.
The theme of fate is used to a quite frightening effect in the film as the victims' fates are sealed once the app tells them their remains time and attempting to escape it will often only result in even more gruesome consequences.
The way that characters are tossed around and dragged by the entity is often startling and shocking.
Quinn looks at Evan's dead body. He had his eyes open. Evan eyes moved and he looked at her.