There are a some incredibly high quality SCPs on that topic of memetics.
A quote from my favorite being;
When that happens, when you make 'eye contact', it kills you. It kills you and it kills anybody who thinks like you.
Physical distance doesn't matter, it's about mental proximity. Anybody with the same ideas, anybody in the same head space.
It kills your collaborators, your whole research team. It kills your parents; it kills your children. You become absent humans,
human-shaped shells surrounding holes in reality. And when it's done, your project is a hole in the ground, and nobody knows
what SCP-3125 is anymore. It is a black hole in antimemetic science, consuming unwary researchers and yielding no information,
only detectable through indirect observation. A true description of what SCP-3125 is, or even an allusion to what it is,
constitutes a containment breach and a lethal indirect cognitohazard.
Basically an 'eldritch thing from outside our reality' that doesn't physically exist in our space, but can interact with it and is the cause of countless other SCPs (giant invisible spiders that no one can directly acknowledge, for example). If you think about "it" too accurately, if you get a good idea of "its" existence, then above occurs. The character who discovers it does so whilst in a container specifically shielded from 'outside' influences, but the moment they step out they basically cause a miniature end of the world scenario, before they just nuke the entire facility, killing themselves, the evidence, and anyone who could've stumbled upon it. No one remembers the facility ever existed.