So is that ghost minotaur supposed to be there the whole time, casting spells? Or is this a bug? You can't do anything about him, and whether or not it is, the odd one-off unkillable of the three mini bosses feels like a bug. My first and lasting reaction to seeing that was that it couldn't have been intended as a feature.

At 1:17:25, he uses his snare aoe while two others channel very powerful attacks, requiring me to be up close and moving. Pretty obnoxious and bad luck.

https://youtu.be/nIO4hWZYr6Y