Ooh this is fun, a great opportunity to learn about a creature I was unfamiliar with! The Layout and presentation is solid, with the only issues being some typos and the darker blotch on the background of page 2 onwards making a few words hard to read. The map is serviceable, but perhaps slightly too dark, some more contrast to it, or a purely black and white one would have worked better, I think!
The structure of the mystery is well done, the scene is set clearly and there is a tense atmosphere painted throughout. The location keys are succinct and informative and just enough info is provided to get this easily parsed and at the table quickly! some more use of italics alongside square brackets would be useful for distinguishing the hidden information a bit more, but what is there works well.
Great stuff!