EDIT: I wrote this after reading the OP, which made it seem like the players had no chance of winning.
Wow, RangerWickett. That sounds like an awesome campaign, and I wish I was in it. Because I love the heroic epic, as a player I'd stand on the ramparts, yell "come and get me!" and make the DM roll out the whole death scene. No way I'm letting that get hand-waved in DM narrative. I'd fight it out to the very bitter -10, and whatever fell powers were at work would pay for every hit-point in blood.
Because that's how meat-shields roll.