Chaos structures.

To clear the map, hire a thief at the beginning, and he will gather resources, capture mines, and generally cause trouble without interference from monsters...

On many maps, the thief can't steal anything; often, a monster is standing in a hidden location or "on a building," so the thief is not very effective.

So, it often looks like this:
To clear the map, hire 2-3 Chaos Mages at the beginning, and they will defeat not-too-strong neutrals. Then, with the appearance of Chaos Devils, any breakthrough becomes quite simple; the question is only about mana.