Played once through for a bit and didn't see what the ultimate goal was until the end when it mentioned taking down the enemy castle. I'm not sure of the exact strategy I was supposed to use except wait until I have enough of the weak little guys to bum rush bigger targets and use them as meat shields for the witch king? Since the witch king couldn't heal (from what I could see) I didn't want to risk him too much or wait too long so I just went around killing random things.
The second time through I tried creating an envoy which didn't seem worth it because they can't attack and it sacrifices 1/5th of your hp. Might not be my kind of game unless it has a slower learning curve with less waiting for units, but I certainly see where it can go in the future with this base system!