So I am, and always will be, a complete sucker for any story that portrays undeath as just a different way of being alive. I love the characterization of the undead king - living, burdened by his duties, separated from humanity by his state yet continuing to feel for his people. You do have a lot of wordcount left to play with, and a dialogue between, say, the king and his high priest, expanding on the description of the ritual, would be a great thing to add, and/or a little more description of the destruction caused by the weapon at the story's climax. But overall a well-done reflection on the costs of war when we unleash powerful weapons.