I'm banking on him having not done that yet since he's probably saving it for his real target and I've not demonstrated anything specific. I'm hoping the death attack will surprise him or make him cast something to count as an undead creature. I suspect it's the turn into undead creature because he is targeting someone that has a special power that doesn't work against undead. If he turns undead and I can target him I can start slamming him with Command Undead spells to get him to retreat/back down.