What about "Horror" in Amnesia?

[Googolplex]

@Scraper

Yes, that's all correct.
Music, atmosphere, sounds and environment are the main things to influence eerieness.

But dead bodys and blood are the second highlight to shock the player.
I was really shocked, if I saw the first corpse on the floor in Black Plague by the laser.
And as I jumped over the laser, the corpse whispered "Help Me".
The corpse in Requiem was so scary, too.

That gives the game a more dangerous atmosphere.