What makes a successful horror game?

[Theory of Games]

Call of Cthulhu's great success is in the SAN trait. The concept that PCs slowly lose their minds when constantly exposed to horror is genius. And it's not about the players being frightened - like most ttrpgs, the focus is the PCs. A group can joke, laugh and have fun while their PCs are scared out of their minds.

SAN is like "mental Hit Points" that dwindle as the PCs experience more and more horror. But with classic HP, once you hit 0, the PC drops. Once SAN hits 0, there's no telling what the now-insane PC will do. I've listened to CoC/DG actual plays where a PC goes mad and causes a TPK or helps cultists summon a Great Old One, destroying the entire planet

That unpredictably of what happens if a PC runs out of SAN is one of the best ttrpg designs ever. IMO a horror game needs to replicate that kind of unpredictably because that's a strong aspect of the horror genre.

 

[Tonguez]

It’s not essential for the PCs to be vulnerable in order to do horror. You can use atmosphere and suggestion to disturb players even when there characters are badass heroes. For example, in a game I ran, when the players realised how the killer had disposed of the body of the clown who ran the apple bob at the carnival, when they realised the irritating “were-hare” NPC had disappeared, and the pie stall was offering rabbit pie, when they discovered iron spikes sticking out of a rocking horse in the haunted orphanage, etc.

Vulnerable doesnt mean weak though, Ripley in Aliens and Dutch in Predator are badass but theyre still vulnerable, even Laurie in Halloween is a bit of a badass. Vulnerable just means that you can lose something - life, friends, sanity, your soul. The disturbing revelations you describe is what builds tension; the horror comes with the loss of sanity or innocence.

 

[Paul Farquhar]

Vulnerable doesnt mean weak though, Ripley in Aliens and Dutch in Predator are badass but theyre still vulnerable, even Laurie in Halloween is a bit of a badass. Vulnerable just means that you can lose something - life, friends, sanity, your soul. The disturbing revelations you describe is what builds tension; the horror comes with the loss of sanity or innocence.

And it quite possible to scare players without them losing anything at all. The person who reads a horror story is in no danger, yet they still feel fear.