In a level-based horror game, it makes sense that a character could become somewhat inoculated against the mental strain inflicted by cosmic horrors. The following rules for mental hardness allow a character to reduce the sanity loss incurred by witnessing horrific scenes and encountered monstrous beings. They are best suited for horror games where campaign-based progression is important to the players and GM and direct conflict with monstrosities is a common event.
Mental Hardness
As a character gains levels, his past experiences with the terrors of the universe allow him to shrug off the weird, mind-bending events he witnesses with greater ease. Having witnessed many shocking sites, he can now accept the gruesome aspects of his investigative work. Mental hardness reduces the sanity lost by encountering a bizarre creature or stumbling upon a gruesome scene. When determining how much sanity a character loses due to a sanity check, whether that check was successful or not, subtract the characters mental hardness from the sanity he lost. Note that mental hardness does not apply to sanity lost by casting spells or other sources that inflict sanity damage without causing a sanity check.
A character's level determines his mental hardness. Divide a character's level by 3, rounding down, to calculate his mental hardness.
Mental Hardness: A New Feat
The following feat, Mental Fortitude, uses the mental hardness rules. If you elect to use mental hardness in your game, this feat can improve a character's ability to shrug off the sanity-melting powers of the mythos. It also makes a good alternative to giving everyone mental hardness based on their level. If you want to give characters the ability to reduce the sanity cost of becoming an investigator by find the level-based application of mental hardness too generous, this feat introduces the concept into your game in much more limited, costly manner.
Mental Fortitude [General]
You maintain your composure in the face of supernatural horrors. This emotional control may result from your experiences in dealing with such terrors or your natural grace and stability.
Benefit: Your mental hardness increases by 1.
Special: You may choose this feat more than once, increasing your mental hardness by 1 each time.