I noticed something significant about medieval armies. Most armies of the era were either conscripted from the populace or mercenaries who fought for coin. However, there were hardly any permanent standing armies to keep the peace when the need arose. What if a permanent standing army existed that was both suitably loyal and undefeatable? An army that will never eat, sleep, tire, or even use the restroom? In addition, this army cannot be killed by any mortal weapon and can overpower numerically superior armies. I am thinking of featuring such an army in my third fantasy book and there will be a battle in which this army fights a force that outnumbers it five to one.