Necropolis – “Dawn from All Sides” [Campaign 2, Mission 3]

Winner, you were the one who suggested it, and that's why, after your advice, I started killing demons. If you don't kill the demons right away, it will be like a time bomb. And when Deleb emerges on the surface with his army, it will be impossible to stop him without significant losses. Moreover, demons are a potential second castle.
And what staffs did you upgrade?