Inferno – “Angel, angel, burning fear” [Campaign 5 – Mission 1]

I don't remember how I completed this battle; it was a long time ago, but there weren't any particular problems, otherwise I would have remembered. :D
2.1.1.0

There are no problems on Easy either.
I tried playing on Hard in the Campaigns, but the AI's stupidity is just annoying. Instead of at least trying to act with its main army, it just sits in the city. Or it passes by my built-up city and goes to another one that is two moves away, doesn't reach it by one unit, and stands there, while I simply teleport there and finish it off. And all the difficulty comes from the lack of resources at the beginning, and a couple of combinations disarm the opponent who acts with two heroes. As for the demonic portal system, I don't even want to talk about it.