The Arbiter is a Halo 2 campaign level in which it introduces the Arbiter Thel 'Vadamee as a playable character for the first time. You must assassinate the Heretic Leader on a Forerunner Gas Mine in Threshold's atmosphere. The mission involves neutralizing Heretic forces. Along the way, the player will have to open a hangar door for reinforcements, fight, for the first time in Halo 2, Sentinels, and fly a Heretic Banshee to escort a friendly Phantom that is looking for where the Heretic Leader escaped to. This is also the first time in Halo 2 you are able to use the Covenant Carbine, the Sentinel Beam, and the Fuel Rod Gun. It is also the first time members of the Covenant aid you. Your allies are Special Operations Elites and Special Operations Grunts, meaning that you start off with rather powerful allies.