A wonderfully weird dungeon crawl, with great layout and a fantastic map.
Favorite thing: a mutation that alters your tongue, described as making it "hard to articulate words. Inmune to toxins." If that's a typo, it's a heck of a happy accident! You might consider taking it a little further, something like, "Inmuthe to thoxins."
Minor quibble: it would be handy if the rumors were marked for the DM with how true they are.