Atlas Games has released an Open Games License version of WaRP, the mechanical part of Over the Edge. (For those who haven’t heard of it, Over the Edge was a tremendously influential role-playing game released 20 years ago. And yes, there’s an anniversary edition.)
The PDF included in the download package is so horribly formatted that I had to slurp it into InDesign and rejigger it just to get something I could stand to look at, and while I was doing that, some half-formed rules popped into my head for handling Call of Cthulhu-style Sanity loss. (Odd, because I never really liked Call of Cthulhu as a game.) They look like this:
Instead of having a Sanity rating that starts out high and gets eroded, we have a Madness rating that starts out low and builds. Each character starts with 0 Madness (though you can start higher if you want, as part of your Flaw).
When your character runs into something horrible, the GM calls for a Madness roll. The GM rolls a number of dice based on the horribleness of the thing you ran into. You pick a Trait to use to oppose this roll, and take a number of penalty dice equal to your Madness.
(I was originally gonna have the GM roll your Madness + horribleness dice, but realized that’d be a pain in the butt for testing multiple characters at once.)
If you fail the roll, two things happen: (1) Your Madness goes up by 1 point, and (2) whatever Trait you used for the Madness roll gets cracked.
What does cracked mean? In fictional terms, it means that your character now has a psychological association between the Trait and the horrible thing. In game-mechanical terms, it means you make a mark next to that Trait on your sheet, and from then on, every time you roll that Trait, one (or more, because your Trait can be cracked more than once) of your dice should be of a distinction color or size. If the distinctive dice roll highest (or among the highest, in the case of ties; and in the case of bonus/penalty dice, we’re only counting the dice you keep for your total), you have to narrate some sort of crazy behavior into your action. This doesn’t have to mean success becoming failure; just that your character is becoming unhinged in some way that comes out sometimes when you use this Trait.
A Trait that has been cracked a number of times equal to its die rating is fully cracked. A character goes fully insane if their Central Trait becomes fully cracked, or if every one of their other, non-Central, Traits becomes fully cracked.
Fringe powers should probably start out with one crack each.