Heretic Leader

Summary
The Heretic Leader is the leader of the heretics, who have made camp on the Gas Mine of Threshold and on Basis, the gas giant and its moon of which Installation 04 rests between. It is believed while the Arbiter was the Supreme Commander, the Heretic Leader was the Lieutenant Second in Command, therefore showing their relationship.

The Heretic Leader is an untrustworthy person in the eyes of the Prophets, and is seen as a traitor, and for that reason, they sent the Arbiter to deal with him. As he attempts to make his escape in a seraph fighter ship, the Arbiter finds him and fights him.

Combat
For all intents and purposes, the Heretic Leader, on his own, is just a Ranger Elite with differently-coloured armour.

However, what makes the fight with him difficult is that he does not fight alone. As seen in the pre-battle cutscene, he creates two holographic doubles to fight alongside him. While these doubles are holographic images, their damage is, strangely enough, all too real.