Demon invasion.

Problem with the first mission. After defeating all the demons (but leaving the green demon's town under his control), I was transported to Grimheim with my entire army, experience, artifacts, and towns, but I lost the mines I had captured there. Because of this, I didn't get the update for the main quests to kill the dwarves and capture their towns, but the cutscenes still played. Now, all the side quests are completed, and there is no one else on the map besides me.