Chosen cliche: Compulsion effect that makes you do bad things/kills you.
The compulsion here is to lie about the existence of the object as best as you can, treating it like an inside joke.
Also for Miku's first challenge.
Also for a challenge Peppers proposed on a discord to introduce something before the conprocs which has diegetic significance.
Originally this was literally a gaslit lamp, but that was too obvious and also you can't stab people with a lantern.
edit March 29th, 2022: happy +500 xbox