Bellicus is the voice of rage and aggression in Alien X. He appeared in the episode "X = Ben + 2" when Ben transformed into Alien X, and Ben quickly discovered he was locked inside the form because of the eternal debates between the two entities who control its body, Serena and Bellicus. He, along with Serena (and by extension Ben), have the ability to warp reality. However, due to Alien X not being able to do anything without a consensus from two of the three parts of its personality,

he is relatively powerless on his own. He is the one who states that Ben is the voice of reason in this part of the transformation. Paradox cannot be 500 light years near him and Serena, or any Celestialsapien for that matter. . Due to his powers, along with those of Serena, he can warp all of reality. However, due to the weakness of the form that Alien X can do nothing unless a consensus is formed between himself, Serena, or Ben, if he chooses to enter the form.