Great concept, I love swamp stuff :-) Nice layout and use of art, though the text is hard to read on some backgrounds. If you have time, it would be great to have a high-contrast version!
I like the exploration procedure, but I think it may take a while to reach 10 (maybe if off-track gave -1 instead of -2, that would help?). I also think it could be cool to incorporate some sort of player agency in the exploration; i.e. once the players realize that navigating the Mirefen is an act of will, they can go faster, or something like that—a way of making it a bit of a puzzle.
I laughed out loud when I saw the reveal of the prince—a perfect mix of fun, gross, and unexpected. I’m not sure I totally understand how the amulet works, but I really like both magic items. Really fun setting, nice work :-)