Having read the rules I can only conclude that rule number eight is a subtle way of telling us to turn against one another for there may only be one mightiest goblin. Rule number 6 must be telling us to be subtle about our actions against one another which in conjunction with rule number 4, which states that we may not kill each other unless both parties agree to the death, seems to imply that we are expected to use some kind of psychological warfare against one another. I guess that makes sense, goblins aren't known for their raw strength after all, so it only stands to reason that the mightiest of them would rely on their minds rather than brute strength.