Anaphex

Nightmare of Anaphex, Sworn to Otzot is a Psion Flayer and devotee of Freeborn Otzot. It is one of the Tier 3 bosses of Nightmare Containment in the Castellum on the Derelict Leviathan, and first appeared in Season of the Haunted.

The final fight starts when Guardians plant the Nightmare Harvester. Anaphex fires explosive Projection Rifle rounds, and getting too close triggers a psionic blast that knocks Guardians into the air. Its shockwave traps Guardians in spherical prisons, which are freed by shooting the large white orbs. At each third of its health it turns invincible and teleports out of the battlefield, and players must defeat three Atavist Illusions, each replaced by an Egregore Atavist, before it returns. This happens twice.

During Season of the Haunted, Tier 3 bosses rotated weekly. The Nightmare Containment page reports that they now change daily.