[Soyweiser]

Frost fiends are great. Super stats, ranged attack, immune to one element, demon (both a plus and a minus, minus anti demon spells, plus, no need to worry about disease, darkness, or supplies), no upkeep.

And they get stronger in cold dominion.

And you should also be able to mass just normal fiends, which are also great. And the normal spine devils, and undead devils (forgot the name) have their uses.