ToME: the Tales of Maj'Eyal

Just wondering if builds relying on Unstoppable to avoid dying from massive damage have some way of dealing with bosses with no mooks around? I mean if it wears out while they still live and you only get back 1 hit point (because there weren't any walking health packs nearby), any hit will kill you afterwards, right?

If you're not going to kill the boss during unstoppable, then you use the last turn to pop a movement/phase door/teleport/etc and get the hell out of there. Then you heal up and try again and/or dodge the boss.