Mythos and Madness
There are several different sets of rules available for dealing with insanity brought on by encounters with servants and artifacts of the Outer Gods, hereafter the mythos. Unfortunately, most of these are best suited to academic characters, not bold adventurers. I am going to introduce the rules from Legendary Games Pathfinder gothic add-on Tomes of Ancient Knowledge, which are designed to be used with Pathfinder and take into account the fact that adventurers are made of sterner stuff than typical Mythos investigators. I will be making a few slight tweaks in order to use some elements from d20 Call of Cthulhu.
These rules add the [mythos] descriptor, and a Sanity Score and Madness Score to each character. The rules only apply to creatures, items or spells with the [mythos] descriptor. Calling and summoning spells that are used to call or summon mythos creatures gain the [mythos] descriptor.
So far the nightgaunts and byakhee are the only [mythos] creatures encountered by the party. Even though the thing-in-a-jar and Antrellus’ Journal are intimately related to the Dark Tapestry, they are not considered mythos items and do not fall under these rules.
Sanity Score: Each character will add a Sanity Score. A character’s Sanity is equal to his level plus 10 minus his highest absolute mental ability score modifier. This is designed to reflect that the horrors of the mythos are more likely to affect the most sensitive and the most brutish of minds. Some examples: a 9th level wizard with Int 19, Wis 10, Cha 10 has a Sanity Score of 15 (9 + 10 – 4(Int bonus)); a 9th level bard with Int 14, Wis 12, Cha 16 has a Score of 16 (9 + 10 – 3(Cha bonus)); and a 9th level barbarian with Int 10, Wis 12, Cha 7 has a Score of 17 (9 +10 -2(Cha penalty)).
An encounter with the mythos may require a Sanity Check, which is a Will save with one of the following DC’s:
Initial contact with a mythos object: DC 20
Reading a mythos tome: DC of tome (20 if none listed)
Learning a mythos spell: 15 + spell level
Casting a mythos spell: 10 + spell level (1)
Encountering a Mythos creature: 10 + CR (2)
Failing a concentration check while casting or maintaining a mythos spell: 20
Rolling a natural one on any die roll related to reading, learning or casting: 20
(1) -1 for each previous successful casting of that spell. Once the DC is equal to 10 no further rolls are required.
(2) -1 for each time after the first that particular creature is encountered. Once the DC is equal to 10 no further rolls are required. Make only one save against the highest CR if multiple Mythos creatures are encountered. For example, the next time Kristiana encounters nightgaunts her Sanity Check DC will be 13 (10 + CR 4 – 1 for one previous encounter). Mythos creatures with a CR 10 or more less than a character’s level do not provoke a Sanity Check. Encounters with advanced Mythos creatures benefit from previous encounters with similar creatures with a lower CR. So, should Kristiana encounter a CR 7 Ngranek Nightgaunt her Sanity Check DC would be 16.
Madness Score: On a failed Sanity Check a character gains one or more Madness Points. Most encounters and initial contact with tomes and items bestow 1 Madness Point. Most tomes give a variable number after they are carefully studied, which is halved on a successful save.
Madness affliction: Every two Madness Points a character has inflicts a cumulative -1 penalty to skill checks based on Intelligence, Wisdom, or Charisma, and to saving throws against mind-affecting effects; this effect is doubled against effects that cause confusion or insanity. Sanity Checks are made at a penalty of -1 for each Madness Point a character has.
Mad Certainty: The penalty for Madness Points is instead applied as a bonus to Knowledge, Spellcraft and Perception checks made to identify or learn about anything with the mythos descriptor, and to the opposed Charisma check to bind a mythos creature. A Madness bonus may also sometimes apply to Diplomacy and Sense Motive checks vs. mythos creatures, and other rolls at the GM’s discretion.
Paranoia: Unfortunately, madness and insanity brought on by the Mythos is subtle and insidious, and characters with a Madness Score or mythos-caused insanity become convinced that they have gained vital insights into the true workings of the cosmos. Such characters do not recognize that they have an affliction and actively resist all attempts at treatment. Characters may not knowingly waive a saving throw or suppress their spell resistance against spells they believe may reduce their Madness Score, even if the spell is harmless, nor will they willingly remove protective items that add bonuses to such saves.
Add a bonus equal to a character’s Madness Points to saving throws against mind-affecting effects used to try to get a character to waive a saving throw or drop spell resistance against an effect intended to reduce Madness Points or cure Madness Point-caused insanity. Characters also add a similar bonus to Sense Motive checks vs. Bluff and the DC of Diplomacy checks aimed at getting the character to lower her defenses against effects intended to reduce or cure Madness or insanity.
Insanity: Once a character’s Madness Points equal her Sanity Score she becomes insane and gains an insanity affliction. An insane character cannot gain any more Madness Points until that insanity is cured. Sanity Points gained while insane are ignored until such time as the insanity is cured.
Regaining Sanity: Madness points may be reduced by use of a restoration spell, which reduces the score by 1 per casting. Using restoration this way requires diamond dust worth 1,000 gp. Heal, greater restoration, miracle and wish can remove all Madness Points. Calm emotions suppresses the effects of Madness Points and accept affliction transfers all Madness Points to the recipient (which are immediately added to any Madness Points the recipient already has). Insanity caused by contact with the mythos may be cured in the same way as normal permanent insanity. A character cured of insanity has his Madness Score reset to 0.
Mythos Lore: Knowledge related to the mythos is most often represented by Knowledge (planes), and Knowledge (planes) may be used to identify mythos creatures and their abilities and weaknesses even if the creature type does not usually fall under Knowledge (planes). Mythos knowledge is carefully guarded, often suppressed and difficult to obtain. Knowledge skill checks made to identify abilities and weaknesses of mythos creatures add +10 to the DC (20 + CR, 15 + CR for “common” mythos creatures, of which there are none, and 25 + CR for unique mythos creatures undocumented in any extant source). Similarly, Knowledge (arcana) and Spellcraft checks made to identify mythos items and spells add +10 to the usual DC (25 + CL for items or SL for spells). Taking a minimum of 10 minutes to reference a relevant mythos tome that a character has previously carefully studied allows a character to double the usual skill check bonus imparted by the tome, if any, to such checks. Characters may never take 10 or take 20 on Knowledge and Spellcraft checks related to creatures, items or spells with the mythos descriptor, even if they have class abilities that would otherwise allow them to do so.