Act Three of Episode Heresy in Destiny 2 tasks you with turning Savathûn and Xivu Arath against each other. There are multiple quests for you to complete to achieve that goal, including the Writ: Misguided Vengeance quest.
In the Writ: Misguided Vengeance quest, you collect runes that bear Savathûn’s mark and plant them on the corpses of Xivu’s forces. The goal is to make Xivu think Savathûn moved against her. There’s even another quest, Mission Dossier: Sibling Squabbles, that does the same but the other way, collecting runes with Xivu’s mark and planting them on Savathûn’s forces.
