As the campaign progresses toward its ultimate denouement, the PCs will increasingly face threats beyond their understanding, horrors that defy comprehension, and deep secrets that sentient humanoids were not meant to know. Therefore, it’s time to introduce some (in)sanity rules.
Sanity is a new ability score. It has the same scale as your other ability scores (like Strength, Dexterity, etc.). Unlike those other ability scores, though, Sanity is calculated mathematically from your existing ability scores. Calculate your maximum Sanity score as (Int + w)/2, rounded down, where w is the ability used to determine your Will defense (that is, the greater of your Wisdom and Charisma).
Sanity also differs from the other ability scores in that it can fluctuate. From time to time, various shocks might cause you to lose Sanity. Therefore, you must track your current Sanity in addition to calculating your maximum Sanity.
Like the other ability scores, Sanity generates a modifier. Use the same formula to determine the modifier (+1 for a Sanity of 12–13, +0 for a Sanity of 10–11, –1 for a Sanity of 8–9, etc.). The modifier is based on your current Sanity score, not your maximum Sanity score.
If your PC suffers a shock that threatens his or her Sanity, the DM will call for a Sanity check. There are three levels of shocks: mild, moderate, and severe. You make a Sanity check the way you would make any other ability check: d20 + 1/2 your level + your Sanity modifier = the check result. Consult the table below to discover how a Sanity check affects your PC.
|Failed||Passed easy DC||Passed medium DC||Passed hard DC|
|Mild shock||Lose 2 Sanity||Lose 1 Sanity||No effect||No effect|
|Moderate shock||Lose 3 Sanity||Lose 2 Sanity||Lose 1 Sanity||No effect|
|Severe shock||Lose 4 Sanity||Lose 3 Sanity||Lose 2 Sanity||Lose 1 Sanity|
If your current Sanity ever drops to 3/4 of your maximum Sanity (round down), you gain an affliction. The affliction is permanent, but its effects vary with severity based on your current Sanity.
|Current Sanity||Affliction Intensity|
|76–100% of maximum||Under control|
|51–75% of maximum||Intermittent|
|26–50% of maximum||Acute|
|1–25% of maximum||Chronic|
When you first gain an affliction, roll on the following table to determine which affliction takes you. The affliction is permanent and cannot be changed. For the sake of gameplay simplicity (as opposed to realism), you can only have one affliction from this table. While your affliction is under control, it has no measurable effects on you. If your affliction is debilitating, you are completely insane and cannot contribute meaningfully to the party. Otherwise, consult the table below for the affliction’s effects.