(I'm new to world building, so apologies if it's not as clean as it could be)
Imagine that you wake up in complete darkness. You're held tightly in a fleshy chamber with sticky and soft walls. As soon as the acid fills your little prison you panic, but right before it becomes too dangerous, you find a hole to crawl out through. It confuses you at first, because stomach's shouldn't have holes like that, but after crawling through this strange intestine like tune, you come to another stomach of much larger size. That stomach connects to 3 other tubes, that connect to hallways that look like blood vessels. You can hear heartbeats from multiple directions and you're pretty sure you went inside a lung more than once on your way.
This is the confusing feeling everyone who ends up in The Body feels. It's a 3-dimensional labyrinth of multiple organs and passageways. No one knows how they ended up here or how it all looks from the outside. Everyone remembers being outside at some point, but how they got here is completely gone from their memory.
You won't be alone though. There doesn't seem to be an end to this alien world, almost as if it's in another universe. Therefore a lot of people fit inside it. A peculiar thing is though, none of the inhabitants look the same. Everyone you will meet in here will be from another world. You will look as much as an alien to them as they do to you.
This world's inhabitants are devided into 2 classes. The settlers and the beasts.
THE BEASTS
Given that everyone is from a different world, There's bound to be some monsters around. These range from a feral dragon living in a giant stomach like it was a volcano, to Giant insects called Gutbugs. Originally there was only one, but it reproduced rapidly and has now infested several hearts and filled them with eggs. Many other monsters exist that haven't even been seen yet.
THE SETTLERS
Settlers call their new home many things depending on their disposition towards it. Most people Just call it The Body. The ones who want to get out call it The Fleshy Prison and the mysterious Church call it The Living World.
The Settlers are doing all they can to survive, preferably by cooperating. Most of them live in a Town-sized ribcage imaginatively called The Ribcage (survivors usually pick effective names rather than imaginative ones) but rumors say there might be other ribcages inside The Body. Whether they are inhabited or even exists at all remains to be seen.
Given that all settlers come from different Universes, culture clashes are imminent, but everyone still mostly manages to work together without needing leaders.
Capitalism still manages to exist even in this retched place. One of the few things people like to eat in this world is Gutbug eggs. While there is no official currency, those eggs are the closest things to it, given that you can trade it for whatever you want. Material to build a house? Workers who will build the house for you? Material, Imagination and Food are all in high demand. And the ones who have it in abundance get to live in luxury.
Gutbug egg salesmen never reveal the locations where they found the eggs, just like how Builders never let people borrow their blueprints.
Another faction among the Settlers worth mentioning is the Church. Given that everyone is trapped within a massive living being, some Settlers have ended up worshipping it. They call it The Living World given that no one has found an end to it, and it must clearly be alive concidering the blood in the still working organs. The monks of The Church claim that worshipping it will help their survival. These monks do tend to survive easier than most, but whether that's luck or actually religious power is uncertain. They also claim there's an Avatar of The Living Body wandering around the vessles. Their goal is to meet this Avatar and ask them about the nature of it's being. However no one has even claimed to see the Avatar yet.
Last ones to mention would be the explorers. They have only one thing in mind. Getting Out! They explore the labyrinth, trying to find an end, but the further they go, the more tunnels they find. Digging through the walls haven't worked either since they don't have the tools to dig through the bone that conveniently always gets in the way.
Part of
MyAltlistArt is not mine, will remove when asked.
(If you want to keep the Eldrich Horror vibes and don't want the mystery ruined, don't check out
Richard_Zall)