The Mage/Seer mental protection anon. I was thinking more along the lines "Things that no mortal should know" or "some unfathomable eldrich shit that cannot be grasped by your average mindreader". But rage players as players SO FULL OF RAGE that going into mental contact with them is traumatizing? Cool stuff.

Ooooh, definitely if it’s something Eldritch and Dark, I could see mind-readers gazing right into the Horrorterrors through the mind of a Seer/Mage of Void. Hell, they may even go Grimdark just from exposure to them. And Rage Players don’t even need to be that full of Rage- Rage is Chaos, Disorder and Anarchy, I could see a mind reader just. Being unable to tell ANYTHING apart from a Rage Player’s Mind because they literally cannot navigate their thoughts coherently.