Caesar John Doukas used the Varangian guard to depose the absent emperor , arrest Empress Eudoxia .
Caesar John Doukas proclaim his nephew , stepson of Diogenes Michael VII , as emperor .
Caesar John Doukas used the Varangian guard to depose the absent emperor , arrest Empress Eudoxia , and proclaim his nephew , stepson of Diogenes Michael VII , as emperor .