Sadly I have not had much time to do or think about RPG stuff lately, but I had kind of a rough week and so naturally I am now feeling creative. This is an idea I've been sitting on in various forms for a while, but it recently mutated (pun intended even though it's not obvious why it's a pun yet) and I like where the idea is heading so I'm just going to write this poorly conceived stream of consciousness version of it now and we'll see what happens.
In some ways on-face it seems maybe more like a PbtA or storygame in that it has a very central theme. That being said, I'm conceiving of it with OSR or that style in mind and I think for reasons I can't totally articulate that it's better that way but there's no reason why someone else couldn't do it a different way.
The core idea is that characters do not die per se; everything is fail forward, for better or worse. Everything is mutilation and mutation and metamorphosis and mind-shattering (maybe Mutations & Mutilations is a better name for the RPG? I'm open to suggestions). There would be lot's of random roll tables for all of these. If you would die, you are reincarnated, or become a ghost, or transcend to some other plane of existence that is perpendicular to the rest of the party. If you would go insane, you enter an alternate state of consciousness, or are consumed by an eldritch being and become the eldritch being, or something like that.
The idea is for the game to be recursive. If you would be critically mutilated, mutated, mind-altered, metamorphosed, etc., you can still be part of the party and progress, just differently. If one player dies or goes insane, they may gain awareness of or access to other realms and dimensions that they can share with the rest of the party that they wouldn't have been able to get to otherwise. It's not just that these things are fail-forward as a fail-safe, but they're the primary means of progression and digression (again, recursive; it is the gameplay loop, not just a way to keep the loop going).
The storygame "theme" of it is that rather than being about body horror or psychological horror or existential cosmic horror, it's about acknowledging these disturbing and sometimes awful changes and accepting them. You could go Adventure Time with it or Always Sunny (the latter being more so why I think it would work better for OSR-style play, if you're following me), or somewhere in the middle.
It's about making mistakes and doing things you regret and accepting them and growing from them and moving forward and then probably doing it again even after you thought you learned better, but in a goofy, ridiculous, tabletop RPG sort of way.
I don't really have the juice right now to write up or consolidate pre-existing tables, but I think the core aspects would be to have these tables, and to have the connective tissue, probably another set of tables, so that once a mutation, mutilation, massacre, etc. occurs, it generates some sort of plot event as well (access to / awareness of a new dimension, a new NPC, a new mcguffin, etc.).