[Endoperez]

I chose Imps & Devil because they fly. It also helps that I can choose where they appear, possibly catching an early enemy by surprise. And I chose Demon Knights because they are cool, and compliment ground army nicely. Flying isn't as great in battle as it is in the strategic map, and almost any nation can support Demon Knights better than flying demons, in thne early game.

It's a pity Spine Devils can't be summoned in greater numbers or with better slaves/soldiers ratio, because they are quite cool.