Affecting Real-Life Sanity

[Roenlond]

One important thing when creating these things: make sure that the player doesn't notice the change. If you for example play a loud crash sound and stuff is broken everywhere once you get back, the player won't be as creeped out as he was already expecting something. It is better for the player just to notice things on their own. "Was that bottle really turned over when I last was in here? I'm not sure. Why is there blood on the floor here? I don't think there was any before, but it could have been"

The insecurity is what makes it scary: if you KNOW that something happened, it just won't be as scary.