Steam Workshop::INTERLOPER's CATALYST [READ DESCRIPTION!]
steamcommunity.com
!!CURSED MAP!!, which will allow you to personally immerse yourself in the investigation of "interlopers", and which can broke your copy of portal 2! :D I'm not kidding, run the map at your own risk and read the descriptions
(Edited)
wait is interloper a creepy pasta or an actual thing, or both?
Its an arg, you should watch it!