So I chose to keep playing, resurrected myself by transforming into a demon, and killed the guards. I went to the castle to confront the king. He didn't have a good explanation for why he tried to kill me, so I killed him and crowned myself King. No one put up a fight and the townspeople bowed before me.
The next day I mounted a dragon, raised an army, and marched on the nearby kingdom. They put up a fight, but I seiged their gate and it fell. I proclaimed myself King of that kingdom too. No one felt like messing with a demon king on a dragon I guess.
I did this again with a third kingdom and then asked the Pope to proclaim me emperor. (I may have been playing too much Crusader Kings 2 recently.)
It was at this point when I had gone so far off-script that the AI pretty much gave up and stopped being able to form sentences.