do /untrap to easily leave the Organism with cheats enabled or check the screenshots for how to build the Access Ritual to enter.
Installing JEI is very much suggested if using versions before 1.11.0.

The mod's backstory:

So...

Ever wanted a forced vacation from your average day on the earth, mining in hell itself, or looting the literal void? Instead to be residing in a flesh purgatory that wails in corrupted pain whilst you tread it's skin and are suffocating the whole time? Well you've come to the right modder's doorstep!

This mod introduces Black Lung, Filtration, a few fleshy paintings, a lot of blocks, Mr. LeaveBlock, and the Organism! (you can just call her Gertrude, no need for formalities!)

Gertrude is not a mob, they're the purgatory dimension I mentioned- Mr. LeaveBlock isn't a mob either.

Also I won't spoil further but when I say purgatory I mean it in the literal sense, but don't fret, you can escape if you work hard enough! It's a challenge, after all.

DISCLAIMER:

FleshCatcher is meant to be a challenge with workarounds. If you do not want to go to the Organism then you do not have to unless you want Receptor or certain blocks. Most fleshy blocks can be made using the Mixing Stand in V1.18+ or the Enrichment Table in old versions, which are expensive to make due to the challenge you would otherwise need to face.

Make sure you check gamerules in V1.17+, it alters dimension behaviors for ease of access. Keybinds should be looked at too in versions before V1.18.

This mod will be continuously but not consistently worked on and updated until I run out of ideas or die of old age/assassin sheriff hired by another modder because "this town ain't big enough for the two of us", whatever comes first.