The most useful monster.

And it's not a given that they'll shoot at each other!:o After all, you can still find someone else on the battlefield! And the undead don't care about fear at all (a ballista - since we're considering archers, and a dragon golem - are worthy competitors! Conclusion: a pile of bones on the floor!:D)! :D
As for useful units, I think blessers are great! :cool: