Recently I had my players read through the Investigator's Handbook in hope that they get familiar with the basic rules and will be more devoted to the game.
Unfortunately, they found this sentence in Chapter 9: Advice for Players
After that, they recall the sentence each time I tell them they are faced with some cultist and would always end up laughing. Certainly it ruined the tension and the horrific atmosphere.
So, is it intended by the rule to allo