Who is Wyglif from Eaters of the Dead: The Manuscript of Ibn Fadlan and what is their importance?

Wyglif is the sickly ruler of the Northmen living near the Volga. He has been removed from the hall to suffer from his ailments in a private hut, which is a custom of the Northmen. After it is determined that Wyglif had no hope of recovery, Buliwyf hovers near the throne, ready to take over once Wyglif dies.