What is the secret formula for scaring someone [No cheap scares!]

[Rapture]

Atmosphere and sounds.
You can put absolutely NO monsters in your custom story, but make it dark as hell and add a few creepy ass sounds and I'll pee my pants. c:

Amen to that

I'd have to agree to that also, stop putting monsters all over your story. Everyone knows how to deal with them, or just flat out dies because they took a wrong turn.

Having the Player live in fear that a monster could pop up anywhere, anytime is more horrifying than having a real one chasing after them.