Arbiter

The Arbiter is the awesome leader of the Sangheili forces. He was once the Supreme Commander of a Covenant Fleet but was disgraced by the Prophet of Truth and made Arbiter. He vowed his vengeance and the Elites rallied by his side when the Prophet betrayed them. He killed Truth and helped Johnny stop Guilty Guilty from destroying the Universe. He now lives on Sangheilios with his pal, the Shitmaster, and his nine thousand million wives.

There was also another Arbiter that discovered a Shield World similar to Requiem, which was infested with Flood. He fought Captain Cutter but was eventually killed by Sergeant 'Awesome' Forge