This is really played up to be based on true events. They even go so far to say that "We still don't know all that went on in this house" or some bullshit. The truth is that this is based on the Mason Family murders at the Tate house.
The entire film only works because of two key elements:
1. The victims are impossibly stupid, easily spooked, and as brave as your average sheep.
2. Magic is real.
The magical killers are able to do things that are simply impossible. They know where the victims are at ALL times. They know what they're doing at ALL times. They know if they're armed or not at ALL times. See a theme here?
It's sad too because this could have been a good film. Decent direction, decent acting (Liv gets all the credit for that), and a not overly ridiculous premise are ruined by piss poor writing.
If you set the tone of your film as being realistic, then I expect the laws of reality to apply.
4 out of 10. (All the points are for Liv and the premise.)