I like a lot of the ideas in here, I think the aesthetic is fun, and the general setup of "walk in quiet, shit hits the fan, weird horror carnage" rocks! The engravings are creepy and well-written, and I think the Function is a very fun concept to be shaped into a mythologically-known concept! I really dig the cover panel as well - I think the title treatment has The Sauce.
Some scattered additional thoughts:
- Text feels pretty cramped to me across the board. An edit pass to size some paragraphs down and give the text frames some breathing room could go a long ways! I'd also recommend switching the body text font on the outside-left panel to the one you got in the rest, and brighten up the body text on the inside to full white.
- I like the room descriptions - they're seeping some good horror flavor! I would love to see some areas of the map, in particular the Lungs and the Prisoner itself, match up a bit more closely with the descriptions.
- I really like all of the creatures described! I would highly recommend unifying the damage dice to d5s/d10s/d100s, since that's sort of the common MoSh style, but their behaviours and the threat they can pose are very effective.
Overall - really excellent foundation! My aesthetic/layout quibbles are supremely fixable and I think the core narrative here is weird, trippy, and very thematic. I'd have a ton of fun playing in or running this trifold, no doubt.