Yeah boss fights are key! I see you are developing in Unity. Are you using any player/content management solutions to simplify things like inventory management, creating shops, etc? 

I have a backend solution for this called Asset Layer (https://www.assetlayer.com/) which plugs into Unity to make everything very simple. It also enables adding some really fun stretch functionality around creator economies and modding. I'd love to connect and show you how it works. I think it could really benefit your game!