Don't rush it; the damage is high, but the speed is low. Knights have a charge attack, speed 7, and 5 less health. It's stronger... definitely stronger than a Rakshasa, a Cave Demon, and even a Wyvern. I don't see anything particularly useful about them... This is the WEAKEST unit of level 6; if you don't believe me, check the statistics in the manual. A Lord always hits and kills one enemy, while the Herald has an activated ability... And 300 militia are twice as good as 300 peasants; let them stay in the city (and pay taxes; why kill them?). The growth rate of a Bone Dragon is the same as for all others. You just need to build a castle and a building that gives +1. If you didn't need to build a castle, the growth rate would be 1, not 2. The green units don't need anything; they have a speed of 8, 50% more damage, 200 health, and high initiative; they hit two at a time. So, one green unit is equal to one and a half Bone Dragons (okay, not two). Special abilities are NOT the reason for the weakness of creatures! True luck can't be ruled out!