Made for the 2025 Onegeon jam. 

System agnostic, but I'll admit I very much had Cairn in mind. There is a bit of Cairn-style character advancement at the end which you are free to ignore. 

This onegeon is entirely about claustrophobia, so don't run it with players who don't want that, obviously.

File is entirely text so should be accessible.

The "room" is risky, but not impossible. I ran some simulations with the Cairn stats and the average player will win more often than not. If you are using a different system you should set the stats for the creature accordingly. In particular, the room is not a trap. It should be extremely clear to the player that they are taking a big risk by entering. The room should reward them twice for taking this risk: first by giving them the meaningful danger they presumably were seeking out, and second, by making them more powerful if they succeed, in a way that directly reflects what they accomplished. If you aren't playing a game where that sort of advancement makes sense, put some cool treasure in the room or something.

I haven't playtested this.

Credits etc

Cover credits: “Bellhole in cave passage ceiling (Hatchet Bay Cave, Eleuthera Island, Bahamas) 8” by James St. John, CC BY 2.0. Cropped and recoloured.

It's been a while since I read Lowlife, but it seems likely some ideas from that have been floating around my brain. If you like this you might like that as well.