As the name implies, this is a library providing a lot of boss utilities so developers can do less coding. It allows for boss battle music (synchronized in the future), more customizable boss bars, minions, staging system and boss spawning (similarly to the Wither).
This library is mainly utilized and developed for Skizzik & Co. but it will have some additional features that I might not need in that mod.
All the information you'll need (including installation) can be found on the Wiki page. For any other issues, please open a new issue in the Issues tab.