Arbiters are possibly the highest known title for an Elite bestowed upon the Hierarchs during a time of great need. Arbiters were sent on various missions: Taming the Hunters, eliminating the Grunt rebellion, obtaining the Index, assassinating the Heretic Leader alongside his followers and re-activating a Forerunner fleet. An Elite is usually made an Arbiter during a great time of crisis such as Thel Vadam's failure to protect Installation 04. It is said that the Arbiters appear to be the will of the Hierarchs as well as their blade.
- Unnamed Arbiter 1: During the taming of the Hunters, an Arbiter was tasked with pacifying the Lekgolo resistance.
- Fal Chavamee: Arbiter during the discovery of the Grunts and the contact with Humanity. His wife was killed by Covenant forces, so he fought off an entire army of Covenant forces. He was killed in a duel with Harka the military assistant for the High Prophets.
- Unnamed Arbiter 2: During the Grunt rebellion, an Arbiter was tasked with quelling the uprising.
- Ripa Moramee: Ripa was an Arbiter who led the Covenant forces on Harvest and assisted the High Prophet of Regret in re-activating the Forerunner fleet. He was killed by Sergeant John Forge in combat alongside his Honor Guards.
- Unnamed Arbiter 3: Fought during the Battle of Jericho VII.
- Unnamed Arbiter 4: Fought during the Fall of Reach.
- Thel Vadam: Thel is the current Arbiter and was responsible for defeating Sesa Refumee alongside his Heretic followers and almost retrieving the Index if he alongside his Sangheili race was betrayed. After his betrayal, Vadam led the Covenant Separatists with Rtas Vadum and Xytan Jar Wattinree and served as John 117's companion towards the end of the Human-Covenant war.