Ancient and unimaginable beings from beyond the stars; monsters made manifest from outside of time; and mortal cultists who worship both, their minds twisted by forbidden knowledge.
Exposure to such horrors can result in madness: While WE might crave both comfort and the truth, only one or the other is possible.
As your investigator discovers more about the Cthulhu Mythos, their mind may become affected and corrupted as they try to reason with things humanity was not meant to know. Measured as Sanity points, your investigator’s resilience to trauma and horror has a bearing on how the shadows of the Cthulhu Mythos haunt their lives. As their perception of reality becomes twisted, they begin to realize the world they thought they knew is a lie.