I agree very much with the idea that it is possible to run a horror game with most systems. The horror is a theme reflected more in the fluff than in the crunch, but even so the system does make some difference.
Initially I also thought about the Fear, Horror, and Madness checks from Ravenloft but I feel that to force the characters to be afraid or horrified is counter-productive. I would prefer to offer rewards for good role playing and to be very deadly so they really fear for their characters.
I like the idea of using Madness checks but along with the drawback of getting insane I would also add some benefit, like an outworldly insight or a psychic wild talent, something flashy that gives them a false sense of hope.
From oWoD I like the use of humanity as a measure to the character´s corruption, and it could be used along something like Ravenloft´s power checks to see if getting a step more near to the darkness is rewarded.
To avoid that the characters are overpowered the level of magic would be rather low and obscure, maybe emulating Carcosa´s by limiting the use of magic to invoke, bind, imprison or torment monsters, adding that when using magic they must take the risk of being negatively affected by it (cursed, deformed, aged, etc).
I’m looking forward to get my hands on these to see how do they do it:
Call of Cthulhu
Chill
Don’t Rest Your Head
Silent Legions
Chronicles of Darkness
Dread
