A really wonderful, immediately accessible 'jump in and play' experience.
The mechanics in battle are simple, but this lets you ignore any learning curve so you can fight the boss enemies and get a feel for the atmosphere of dragon bones animations in action.
Personally I think that makes this project perfect for its purposes.
With that in mind, the boss's look awesome and hopefully inspire you to check out more of this artists amazing contributions for RPG Maker and enemy variety in general (as written in the terms of use these aren't limited to RPG maker, and you can already find some prepared in the Unity asset store).