Good stuff, had a lot of fun with this one, here's some bugs and "bugs" that I found.
Yunder might have a slightly dodgy hitbox. I've several times been caught by him when it felt like I shouldn't have (maybe he just has more reach though?) And he once had a stick of dynamite phase through him.
When there's multiples of the same enemy type you often get them saying the same line overlapping each other and they also often walk the same route basically inside each other. There should probably be some override to prevent these two things from happening. To be honest, this is another thing I've just seen happen with Yunder, and it was in the maize maze level, the challenge version where there's three of him.