insanity

It's also possible that Link is referring to the insanity score used by the madness domain, and by some of the Bleak Cabal feats. There's a decent rundown of how that works in the PSCS 3.5 Feats section with the Bleaker feats

If I recall correctly, Fear effects were temporary and short-term. Horror was usually temporary, but much longer-term. Things like memory blackouts, terrible recurring nightmares, and constant depression. Madness was permanent, and entailed a drastic change to a character's psyche. Some of it was the usual babbling schizophrenia, but I think a few effects were more interesting. Like hallucinations, loss of an alignment concept (e.g. no sense of good and evil) or totally altered memory of most events.

I don't have the books with me at the moment, so some of that may have been my own invention. Still, hope ya find it useful.

The tricky thing with sanity and Planescape is that sanity is basically a comparison between what a person believes to be real and what is actually real. However in PS what a person believes to be real in a limited fashion and what others believe to be real, really IS real.

Thus a person is only really insane if they believe themselves to be so, or a great many others believe they are.

Or, what you're saying is, they're Xaositects, right?

To contribute: Sanity on the planes would be a tricky proposition. Who can tell their kids "There are no monsters..." when daddy just died from a pit fiend's firey aura two days ago? I would think the sanity rules would be great for primers on the planes, but planar characters should get bonuses to reflect the fact that they've grown up with and seen just about everything...they don't have to take it on faith alone that demons and Tanar'ri exist, they just have to visit the Friendly Fiend .

There is no God!

>>Ravenloft Player Handbook (3.5 Ed Rules)

Fear: 5d6 Rounds, worst effect: Panic
Horror: between 1 week (minor) and 30 days (major), but you need to pass a new horror-check to end the effect. worst effect: system shock (3d6 con dmg)
Madness: ends when all ability points lost to madness are regained, worst effects: amnesia (negative levels), suicidal thoughts (must attempt suicide after the next failed fear, horror or madness check)<<

Yeah, I'd recommend looking at the 2E rules for Ravenloft. Like 90% of the material in 2E, they were better. (3+ had better/more skills, I'll give it that, but what gm hadn't home ruled in more skills for 2E by then anyway?)