Sanity is an important mechanic in Cthulhu's Tabletop, as players must grapple with the horror and otherworldly occurrences of the Lovecraftian universe.

Determine maximum sanity

 Each character has a maximum sanity score, which represents their mental stability and resilience to the horrors of the Lovecraftian universe. This score is determined by the character's Constitution and Education attributes, as well as any sanity bonuses or penalties they may have.

Lose sanity

As characters encounter and witness unsettling or otherworldly events, they may lose sanity points. The GM should decide how much sanity a character loses based on the severity of the event and the character's reactions to it.

Check for sanity loss

 Whenever a character witnesses or experiences something that might cause them to lose sanity, the GM should have them make a Sanity roll. This is usually a percentile roll, with the character's Sanity score being the target number. If the roll fails, the character loses sanity points.

Insanity effects

 If a character's sanity drops to zero or below, they suffer from insanity. The GM should decide on the specific effects of insanity, which could include hallucinations, delusions, phobias, or other mental disturbances.

Recover sanity

 Characters can recover lost sanity through rest, therapy, or other methods. The GM can decide on the specifics of how much sanity a character can recover and under what circumstances.