Wulf was the son of Freca, who tried to force a wedding between Wulf and the daughter of the King of Rohan, Helm Hammerhand. Helm killed Freca, and Wulf took charge of a Dunlending army that overran Rohan with assistance from the Easterlings and Corsairs of Umbar. Wulf took Edoras, and besieged the Rohirrim at the Hornburg in the refuge which would later be called Helm's Deep.
Wulf's Dunlending army managed to kill Helm's sons Haleth and Háma, and the king himself perished of grief and exposure. But Wulf was in turn killed by Helm's nephew Fréaláf Hildeson, who with the aid of Gondor reclaimed Rohan for the Rohirrim.
Portrayal in adaptations
In Middle-earth: Shadow of War, Wulf is depicted as forcing the marriage himself and nearly killing Helm Hammerhand in the process. Helm took a Ring of Power from Sauron to restore himself and to march on Wulf's hall, where in his rage, he killed Wulf and, accidentally, his own daughter and all his soldiers. He was portrayed by Liam O'Brien, credited as "Daughter's Suitor."