A character with ranks in this skill can function as a scholar on the topic of the Cthulhu Mythos, using this skill in place of Knowledge checks or Spellcraft checks made to interpret, understand, identify, or learn about Cthulhu-related topics. It can also be used in place of any skill used to cast rituals.
Gaining ranks in this skill strains the minds of most mortals. You take a –1 penalty on saving throws against dread, insanity, and confusion if you have at least 1 rank. The penalty increases by 1 for every 5 ranks you have (for instance, 10 ranks gives you a -2 penalty, 15 ranks a -3 penalty, etc).
Sandy Petersen’s Cthulhu Mythos, © 2017, Petersen Games; Authors: Sandy Petersen, Arthur Petersen, Ian Starcher.