Zavulon

(Also spelled Zabulon) (Grand Dark Mage) - An ancient schemer about the same age as Geser. He runs the Day Watch in Moscow and his plans frequently involve misdirection and hidden agendas. His power seems to rival that of Geser but he is often, if not overpowered by Geser, outwitted by him. His true form has taken on demonic characteristics because he has spent a great deal of time in the Twilight. His chosen human appearance is often misleading, as he appears as a thin intellectual who does not seem to be a threat to those who do not know him.

Day Watch Novel
Geser's consistent ability to outwit him eventually forces the outside forces of the gloom to step in and restore the balance between Light and Dark.

Face of the Dark Palmira
His human name is revealed to be Arthur. The name "Zabulon" is from the Old Testament.