It does serve a purpose, just not a huge one. It gets you more loot money and later you get upgrades that give you mana after fucking themAlright, in addition to the controls being bad, the game doesn't explain anything. It wasn't "a priestess", it had to be a specific one. And I while you have to cast mind break on the regular ones, this one you had to "kill" for some reason. Also mindbreaking the regular ones apparently serves no purpose, since they just vanish after you exit the map by the looks of it.