The Spiritcaller from my Harder Illage and Spillage mod. List of changes can be found on the mod page
Mod page: curseforge.com/minecraft/mc-mods/harder-illage-and-spillage
Also yes I couldn't beat him in the vid. For some reason the way this fight works just doesn't click with my brain. I've beaten him off camera before and he's not that hard I promise (and now that I think about it blast protection armor would be really good)