The Helm of Domination (also referred to as the helm of the Lich King or Lich King’s crown) was crafted by demons, both to hold the spirit of Ner’zhul and grant him his Lich King powers. The helm, which helps command undead and others, was bonded to Ner’zhul’s spirit and locked within the Frozen Throne. The runeblade Frostmourne was also locked inside the Frozen Throne, but Ner’zhul cast it from the throne so it would eventually find its way to Arthas. Upon shattering the Frozen Throne, he donned the helm and inherited the Lich King’s powers. It forces the undead Scourge to obey the wearer’s will. With death of Arthas, the Helm of Domination passed to Bolvar Fordragon, who became the new Lich King.