As March, and my theme of March Madness draws to a close, I feel like I would be remiss if I didn't spend some time talking about the sanity rules from the d20 SRD. I believe these rules were originally part of the D20 Cthulhu game, written by Monte Cook and John Tynes, and published way back in the mists of time (2002) by Wizards of the Coast. I'm not going to do a full review of these rules, but let's go ahead and take a look at some of the interesting bits.
For starters, these rules are the most comprehensive rues for tracking sanity and madness that I have looked at so far this month. So if you are looking to run a game with a Cthulhu theme or a heavy emphasis on madness over the course of an entire campaign you definitely want to take a look at these rules.
One major difference between these rules and the other systems I have looked at is the way sanity (or insanity) is tracked. In the various other systems I've looked at, traumatic events and the like could cause characters to gain a number of corruption points or despair points or something to that effect. In this system, however, characters start with a pool of Sanity points that they can then lose over the course of the game. Right up front this gives Sanity a piece of real-estate on your player's character sheets, letting them know that they will probably be going insane at some point.
And make no mistake - if you use these rules then it is a question of when, rather than if, characters will go insane.
Each character starts with a number of sanity points equal to their Wisdom x5. I get why Wisdom makes sense here, but I can also see how one could make an argument for Charisma or even Intelligence being the deciding factor as well. That's probably a tangent for another time though.
To make a sanity check, one must roll percentile dice and score equal to or less than their current sanity score to succeed, meaning they lose only 1 or 2 sanity (or possibly none), rather than something like d4, d6 or d10 sanity - depending on what sort of awfulness they've seen. Gaining - and regaining - sanity is a much slower and more difficult affair. Short of a few magical means, you will gain d6 sanity points each time you go up a level, or if you are being treated by someone with the Heal (Medicine) skill you can regain 1 sanity point per day of care. Unless they roll a 1 on their skill check, in which case you lose a point of sanity.
So basically, right right from the start these rules set up a battle of attrition that your characters are probably not going to win, and there are lots of rules for what sort of awful things will keep happening to them as they keep losing. There are rules for temporary insanity, indefinite insanity, and permanent insanity, and on a long enough timeline your characters will surely get to experience all of these.
This is a fairly robust system with lots of rules and optional rules for what triggers sanity checks, including things like watching your friends get murdered, reading "forbidden tomes," or just seeing a really scary monster. There are many charts and tables that show what causes sanity loss and how much it causes, and even more charts and tables that show you what happens as you lose sanity, and just how exactly your crazy manifests. There is a lot here, so there is of course some extra bookkeeping that goes with using these rules, but it's mostly intuitive and printing out a few charts should help keep you from going crazy trying to remember everything.
If you want to run a one shot adventure featuring madness, I recommend using either the suggestions from the DMG or the corruption rules that I talk about here or, for something a little more involved but still self-contained, the rules for The King's Mercy. In either case you could still use the madness tables from the SRD to supplement they madness effects that characters suffered, and the examples given here for what sort of things could trigger a sanity check might also be useful. However, if you want to run a campaign with an air of desperation, where the characters exist in a bleak world and are living on borrowed time, where the best thing they can hope for is to maybe beat back the darkness just a little bit before they lose their minds, then these rules are probably for you.