Sesa 'Refumee
From Halopedia, the Halo wiki
The heretic leader (Sese 'Refumee) and those around him learn the truth about the Halo network from 343 Guilty Spark, and rebel against the Covenant shortly prior to the Civil War phase of the Human-Covenant War. They establish their base, an independent faction on a Forerunner research station in the atmosphere of Threshold, the gas giant that Installation 04 orbited. Just before Covenant SpecOps units led by the Arbiter storm the base, the Flood stored on the station escape and almost overrun both the Heretics and the loyal Covenant.
The Heretic Leader and the elites under his command do not wear normal Elite armor, rather they wear a chest plate, a respirator in the mouth, and rounded goggles. The heretic leader also has a jet-pack on his armor. Also, the Grunts under his command do not wear the large pointed air-tank that Covenant grunts normally wear; rather they wear a much smaller H-shaped backpack with several methane tanks attached.
The heretic leader is fond of using holodrones to both communicate and serve as distractions in combat. However, the Arbiter bests him regardless. In the course of his defeat, the heretic leader gives the Arbiter hints that Halo's purpose is destruction, not salvation, a truth Arbiter finally confirms for himself at the end of the game.
The Heretic Leader is voiced by Miguel Ferrer.
