Duma is currently a dyad and was a higher angel who was expelled into the Ether. When Julian pulled him down with the amphora, he became a Dyad with Edward Riesen. Originally, Edward being the dominant spirit, the dyad was manipulated (by a corrupted Gabriel) into having Duma become the dominant spirit, taking over more control. Duma is currently the supreme ruler of Vega, after an Eight-Ball takeover.
Duma is a stone cold soldier. He has little regard for human life; he was willing to kill all the humans inside Vega if he didn't get his wishes of seeing the Chosen One. He is trigger happy, looking to kill and eventually does, kill Claire Riesen and other soldiers. He becomes the supreme ruler over an Eight-Ball-run Vega, possibly subjecting the few humans that are left within the city.