Thel 'Vadam normally referred to as just "The Arbiter" is the secondary protagonist of Halo 2 and a supporting protagonist of Halo 3. He played a large role in the destruction of the Covenant Empire and the defeat of The Flood. At first he is strictly loyal to the Prophets but after an assassination attempt fails on him ordered by the Prophets, he allies with the humans and even becomes a good friend of Master chief.
Halo Combat evolved Edit
Although he did not appear in Halo combat evolved he was Supreme commander of the fleet present on installation 04 and because his failure to stop the installation from being destroyed the prophets held him responsible.