The Ashdurbúk (Or. "Sole Ruler") was the High Chieftain or King of the Orcs of the North and the Lord of Gundabad, the northern Orcs' holy capital. The Ashdurbúks were traditionally of the lineage of Mukarg, one of Morgoth's orcish generals of the First Age. The Ashdurbúks were also the keepers of the Ûlukai and supervised religious rituals. They still recognized the authority of Sauron and paid him tribute; in return, the Dark Lord allowed them to rule their kingdom in his name.
Ashdurbúk-Zalg's full title was "Ashdurbúk of the Thirty Tribes, Overlord of Gundabad, Lord of the North, and Tyrant of the Mountains".