Necromancer – “Invasion” [Campaign 3, Mission 3]

I don't understand. This time, I was playing 3.0, and Cyrus was defeated right after taking the second magic city, so he's essentially gone for the orange faction. All quests are completed, and Isabel and Markel have reached level 26. Markel is progressing through the third garrison on his way to the last magic city, and then the game freezes. Is it because Cyrus is gone, or because Markel's army has 34 spectral dragons instead of bone dragons? What do you think? Also, Cyrus attacked on his own, but he was killed in an autobattle with "medium" danger at that point in the game.