The Arbiter

Thel 'Vadam, once a powerful Supreme Commander within the forces of the Covenant, upon his failure to protect Halo, 'Vadam's power was taken, but was offered a chance to continue serving as the Arbiter, taking missions likely to result in death. When the truth of the Halo installations by the Gravemind and the Master Chief, who he knew as 'The Demon', he began to question the belief of the Covenant, and thus revolted against the Prophets of the Covenant, assisting the Master Chief to force a powerful blow against the Covenant forces. Later on, Thel 'Vadam known as the Arbiter led the Swords of Sangheilios along with Rtas 'Vadum.