“Ashes’ Will” – “A Sad Journey” [Campaign 2, Mission 2]

Let's do this: I'll describe how it went for me, and you can compare and perhaps find the cause of the problem based on the differences. I was playing on a pirated copy; I conquered the cities in the following order: Necropolis to the west of my starting city, then the Academy south of that Necropolis (at the time of conquest, both cities were neutral, meaning they hadn't been conquered by anyone yet), then (to the east) the orange player's Academy (and as a result, the orange player was defeated, and the completion of one of the main quests was marked), then a chase began across the map with the yellow player, who was far from a pushover, but it all ended with the complete defeat of the yellow player in his home Academy, which is in the southeast. Next, through the Dungeon to the red player (along the way, we defeat the Demon Lord, thus completing the quest), and finally, we kill the last of the opponents. Mission complete.
Before capturing the first of the cities, I received a quest about vampires, but I didn't complete it.