Bellicus

Bellicus is Alien X's voice of rage and aggression.

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 is not allowed to be closer than 500 light years to him and Serena, or any Celestialsapien for that matter.

Alien Force

 * X = Ben + 2

Ultimate Alien

 * The Forge of Creation
 * The Ultimate Enemy: Part 2 (Flashback)

Ben 10 Alien Force: Vilgax Attacks
Ben got him and Serena to allow him to control Alien X before Vilgax took over the world.

Trivia

 * Bellicus' name seems to derived or based off "Belligerent" or "Bellicose", meaning very eager to fight, which describes much of Bellicus' personality.
 * He seems to have a fondness of the dinosaurs, as he tried to persuade Ben into preventing their extinction in X = Ben + 2.
 * His tabled motion to save the dinosaurs was argument number 80 million and 3 (80,000,003).