Ever-expanding bunker

A world building project that began on the subreddit /r/politicalcompassmemes in 2020 but soon got its own forum (/r/everexpandingbunker) and two separate wikis (on Miraheze and Wikia.) One of the few good things to have come out of Reddit.
The In the universe of the Bunker, a giant transdimensional monster called the Mire made the surface of the earth uninhabitable (the coming of the Mire is called the “Event”), so all of humanity retreated into a 4,000-floor bunker that is constantly being expanded to make room for more inhabitants. A computer governs the entirety of society with an iron fist, and it was programmed to keep humanity alive at all costs. Due to the advancing “Flesh” that consumes all who touch it in the Bunker’s “low levels”, people only venture in the top 500 or so “levels”, and even fewer levels are inhabited. An entity known as “the Bogs” representing man’s greed resides deep below.

BUNKER SOCIETY
Several factions and sects exist within the bunker, like the “Eventists” who believe that the “Event” was a lie or severely exaggerated, worshippers of Ronald McDonald (the “foodclown”), Bogs-worshippers, insane “foom”-addicted “whirlers” who dwell in the darkness of the lower levels, the I.R.O.N. gym dudes, surface-disbelievers, those who believe that humanity will reside in the Bunker forever, among other sects. Some people have also escaped the bunker to live on the Earth’s surface, which is said to be an icy wasteland in some canons and extra-hot in others.

The ever-expanding bunker is a total rabbithole that will keep you up all night and scare the crap out of you.