Uhh it is noble district... in old tarantia
Found a way to kill the caster boss. If you run out of her room and to the right down the hall. There is a barrel in the middle of this hallway, wait around the corner till the boss is right in front of the barrel and go explode it. It will get her down to 14-28%. From there you actually have to kill her. So stuns and heals.
Its there...