Safe zones strengthen your light.
Balwûr is a Hive Wizard that is one of three possible weekly encounters summoned from an Antiquated Rune. Balwûr was also the daughter of Savathûn.[1]
Tactics
Balwûr's presence alone keeps the mist on the Court of Oryx in most places, except under the platform at the Court of Oryx, where a safe zone is present. She spawns Acolytes of Balwûr around the Court, which cannot be killed unless a Guardian is in a safe zone. On killing it, a temporary safe zone is created outside the underside of the platform. While Guardians are in that temporary safe zone, they can deal damage to Balwûr.