Heretic Sangheili encountered in Halo 2 are the Sangheili of the artifact retrieval group led by Sesa 'Refumee. When 'Refumee discovered the truth about the Halos, his Elites followed him in the rebellion against the High Prophets, knowing what the Halo Installations would do if they continued The Great Journey. They used the Gas Mine above Threshold as a base, and placed Banshees and at least one Seraphs starfighter as an "Air Force" to defend the mine. They also set up a makeshift camp on Basis, Threshold's moon.
The Heretic Sangheili do what they can to stand out against the rest of the Covenant.
They have a limited Rank System, consisting of:
Heretic Sangheili do not wear combat helmets like their Covenant counterparts do, but instead don breathing apparatus to assist in respiration on the Gas Mining facility. Heretic Sangheili also have four fins on the back of their armor, similar to the traditional armor seen on Ripa 'Moramee's clan brothers in Halo Wars: Genesis. Sesa 'Refumee does not share these fins, but instead has a jet pack on his back nearly identical to those used by Ranger Elites.
Heretic Elites can be found in both brown and gold armored variants, as well as the Heretic Leader's personal red-colored armor. Sangheili who wear gold armor are the equivalent of Elite Majors with more health and stronger shields, while those with brown armor seem similar to Elite Minors.
They mostly use Carbines, Sentinel Beam, and also Energy Swords, but are never seen using Plasma Grenades. Plasma Rifles are only used by Heretic Banshee pilots and the Heretic leader. This most likely originates from the fact that the Heretics want to shun the Prophet-given plasma weapons and further themselves from the Covenant's Great Journey.
The energy shields of the gold Heretics are as strong as a Major's, while the energy shields of the brown ones are as strong as a Minor's. Note that their shields glow purple instead of the blue that Covenant-loyal Sangheili use.
- A glitch causes the melee attacks of Heretic Sangheili to have little or no effect, unless they are wielding Energy Swords. However, their melee attacks have a small chance of hitting when standing to the left of the Sangheili.
- The Heretic Sangheili is one of the least used Bipeds, sharing their inactivity with the Heretic Unggoy, in the Halo trilogy, as it only appears on two levels.
- In the level The Oracle, there is a Sangheili using a Needler, which is odd because they use Carbines and Energy Swords mostly. This is the only Heretic Elite seen using a Needler and note he only appears a few times, not always.
- You can disarm a Heretic Sangheili by throwing a Plasma Grenade on it while the Mythic skull is active. Once they drop their weapon they charge at you using the sword animation, but will not hurt you. If you have any allies they will shoot the disarmed Heretic.
- A class of Elite known as "Heretics" appear in Halo: Reach. These are actually just Elites using Human weapons, rather than rebels. They only appear in Firefight.
- With the Assassins Skull turned on, causing all enemies to be invisible, the Heretic Sangheili's eyes will still be visible.
- Sesa 'Refumee- Heretic Leader