History of Hiraks

Hiraks, the Mindbender is a Scorn Baron fought in the Kell's Fall Exotic mission, in the Revenant Plane. You get a Refracting buff of about two minutes; when it expires a Shattering debuff damages you and eventually kills you.

Fight

1. He summons Hive and Scorn units and uses Void Ether-Shields that negate damage.
2. After losing about a third of his health he retreats to the material plane; you fight Thrall waves and light three braziers (one in the Revenant Plane, two in reality).
3. At two thirds he teleports to the Sanctum and you follow through another mirror; Araskes may help.

He uses an Arc Scorn Boomer as his weapon (per Destinypedia).