Helm Hammerhand was an ancient king of Rohan. A grim man of great strength, Helm was powerful, but he did not suffer fools gladly. When the powerful warlord Siric demanded Helm's daughter Bernwyn in marriage, he was denied. A week later, Siric ambushed Helm and abducted Bernwyn. Near death, Helm was offered a Ring of Power by Sauron and Celebrimbor. Returned to life and fueled by vengeance, he besieged Siric's fortress and in his rage, struck and killed his own daughter.
He became consumed in fury and by the Ring of Power, transforming him into a Nazgûl, one of Sauron's best servants.