There's also a plus: Duncan just stands near the city. The main thing is to capture three castles right away. The heroes you encounter are weak, but they can cause trouble. That's why we use the second hero. We leave swordsmen in the mines and enjoy life.
In my final battle, 900 militia played a decisive role. We rush the knights to the gates, eliminate the knights that fall from there, and so on, until our own are gone. During this time, we destroy the royal griffons attacking from the sky and bring zealots and others to the gates (in my case, militia). We cast watch spells, prayers, etc., sneak up on the archers, and extinguish the light...