So far the plan is to have a series of weeks with different weather conditions creating varied behaviors. At the end of these respective weeks the player faces off with a boss. Each one supporting the theme of the weather of that week. Here you can see a first pass of those concepts.
I think several of these will make it into the final game once they are colored up and broken down a bit more to allow for animations. The only one missing is a proper frosty boss with corresponding snowflakes. We should have some color art this weekend which I am very excited about.