Wait, Mythic characters become "Immortal" at Tier 9. But there are certain methods of killing them that do work.
Is it possible that Deskari might have to kill the PCs more then once? Because it might lead to the party having to keep "re-spawning" and coming back, which has the potential to be either hilarious or annoying.
good point. Remember also that demon lords respawn as well. so as long as Deskari can survive a year after the PCs kill him the first time it could become an eternal battle of some sort