A good amount of Themis unlockable spells cause an error, some don't do anything but there a couple spells that cause them to take no damage from then on with their remaining health becoming undefined and attacks also. Most of time the issue happens in Arena but occasionally happens outside of it.
After you lose the fight they also automatically progress to the next stage.
minotaur is also missing dialogue when you try to fight them in their 2nd and 3rd stage.
This is for V0.2.5