It dawned on my as a pondered how to recreate the stress mechanics. Typical caveats for the poor and unrealistic treatment of mental illness apply.
Sanities Shall Be Splintered
(yet another incomplete, proposed mechanic, with root concept from Trollsmyth's Shields Shall be Splintered)
Upon taking a hit, a player may choose to sacrifice the character's mental well being instead of losing hit points. The character must make a save vs death (or wisdom, psionics, etc depending on your ruleset and preference):
- If successful, the character sustains no damage but will have a temporary (but cumulative) -1 to further saves for Sanities Shall Be Splintered until 8 hours of restful sleep had been had.
- If failed, the character gains a temporary insanity (from the AD&D Dungeon Master's Guide, p83, or your preferred edition of Call/Trail of Cthulhu). The insanity can be "cured" by a week spent in medition, prayer, flagellation, or preferred debauchery at a cost of 100 gp / character level. The character also suffers the side affect of success listed above.
This is my first draft, conceived as a type. The next revision will probably have results for a save of 1 (and positive revelations for a roll of 20). Maybe spell loss, wisdom penalty, or something similar would be more appropriate.