Coup de Grâce
Configure the Lure to hunt the High Celebrant. Then complete the Coup de Grâce mission in the Dreaming City.
It is time to put an end to Xivu Arath's High Celebrant. Work with Crow to draw the creature out of its Dreaming City lair, then finish it off for the last time.
"Xivu Arath needs her High Celebrant to create Wrathborn. Stop it and you stop her… for a time." —Osiris