Damn. This really, really good. Unsurprising, because you've assembled a crack team of experts to assist. But I love the premise, the writing, all the creepy skin stuff. This feels very playable, and very Appendix N. It would also fit really well into the UVG or Vaarn, places I am fond of.
Gus's maps are fantastic. The non-cutaway map makes a great cover.
If you were to expand on this (which I rather think you should!), some more art and ornament to set the tone would be great--but obviously we were very space-constrained in this jam.