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Then I don't know. There were no single-player maps in the beta :(. Most likely, it's the same as in the campaign - you can make the starting hero a warrior or a mage, but the face will remain "story-based".
How could there not be? There were single-player maps in the beta.
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I already asked this question above, in general, the problem is this - in a skirmish, I can't choose a hero, I have a hero from a human castle, and that's it, but I can choose opponents.
Try a different map.