From the description in the rules
This is not a game about grace or style; it is a game about grabbing gold and then more gold! To find gold, you need to be victorious in battles. You win your battles by means of creatures that also find gold if you win the battle. You need to roll high to win your battles, but you need to roll low to find any additional gold.
Thus, creatures are the most important part of this game. You cannot do battle without them, and you cannot find gold without them.
It is quite possible to be nice to the others while playing. Then again, you don't have to. You probably shouldn't - for those who don't play nice and fair tend to win more often, just as in real life.