Heimerdinger Presents:
The Mist did not just subsume Atreus, but also resurrected the long-dead spirit of Pantheon: the old Aspect of War himself. With Atreus' stubborn defiance silenced, Pantheon can resume control and revel in battle once again. It doesn't matter to him whose banner he fights under. If that banner is the Ruined King's? So be it.