"Weak demons"??

If the hero is Nimue, then some serious reinforcements will appear, and that's when the opponent might get into trouble, and you don't have to worry about your own troops anymore. At the beginning, the demon boosts attack (after its initial skill, and it's best to take a tactic skill), then you can choose either magic or luck. I don't like machines myself; I take leadership or luck if I can't get anything else (together with attack, it works out great) + darkness.