'Arguments are soldiers' and 'reason is for persuasion'; hence, you obviously use biasemons on your opponents to make them make bad decisions and believe wrong things.
(It's not any more malicious than enslaving wild animals and making them fight until they are knocked unconscious by the trauma...)
Hey rationality friends, I just made this FAQ for the credence calibration game. So if you have people you'd like to introduce to it --- for example, to get them used to thinking of belief strengths as probabilities --- now is a good time :)