Take a look at this drawing. I drew this over a year and a half ago:
I'm mentioning this because even then I drew it with the idea of using it as a base for a level in this game. Take a look at the original post of this drawing, if you want to see how I drew it: original post
The game was in very early stages back then, so naturally a lot has changed now that I finally worked my way up to starting on this level for real. Here is a work in progress of it now. I expanded accessible places, added paths in the surrounding ground/flesh and so on:
The gray background is very much still not done, so don't pay too much attention to that. This whole area is in a different style from the rest of the game so far, so there are quite a few things I still need to work out about integrating this linework style on top of painted background. All the dark blue and dark red areas are walkable, everything else will count as walls. Over the last few days I also added more linework to raise the detail