The Hunt of Suthrikorn
For complete rules see here
Your starting sanity (abbreviated SAN) is 5 * WIS, wisdom score not modifier. So a character with 13 WIS has a starting sanity of 65. Your max SAN score is 99 – Knowledge:Forbidden Lore (explained later). A character with 10 or less SAN is aware they are nearing complete insanity. When a character reaches 0 SAN they become unstable and start losing 1 point per round, a full round heal check (DC 15) stabilizes the character. Upon reaching -10 SAN the character becomes permanently insane and an NPC. A Sanity check is made by the player rolling a d% and if the number is higher than your current sanity the check fails.
Knowledge: Forbidden Lore
This is like any other knowledge skill, certain creatures(DM discretion) fall under this category. Skill points can’t be spent for this skill, thus it may be used untrained. Reading certain tomes will increase this score and consequently decrees your maximum sanity.
Upon leveling you gain 1d6 sanity. Receiving personal care outside of battle can also restore sanity slowly.
Loss of Sanity
A character loses sanity primarily by witnessing horrific scenes or casting spells. Most sanity loss from casting spells is small but the more powerful the spell the higher the sanity cost. Spells with the [Evil] descriptor cost more sanity and [Necromancy] spells cost even more. Certain tomes also cause sanity loss, see below.
When a character loses sanity equal to 1/2 * WIS from a single episode they go temporarily insane for as short as 5 rounds to as long as 4 days. If a character loses sanity equal to 1/5 * their current sanity in the space of 1 hour they go indefinitely insane for a period of 1d6 months but may still be playable.