Zephyr went first. Seeing that she couldn't cast spells, Biara started fighting with her hands. The battle became like a fight with neutral creatures. 500 units of level 7, with active magical support from Zephyr, easily defeated the enemy.
I'm still not very familiar with the mechanics of version 3.0. I haven't studied Inferno at all. It seems that archdevils and archdemons don't have immunity to spells that affect the mind. However, I couldn't cast either charm or berserk on them.