Kaos

According to X, Kaos was once the greatest warrior in the Empire, being picked first by the Emperor himself. He has since retired, taking his B't L'Amour with him, which the Empire allowed because of his past service. During his time with the Empire, Kaos realized that the B't are being used as mere weapons to achieve the Emperor's goals. He wished to rebel but was too old and weak to do so, instead decided to wait for a younger warrior to fulfill this cause. His hope of rebellion was rekindled upon hearing of Teppei Takamiya and how he revived X.