King of Durin's Folk was the title given to the head of Dwarven clan of Durin's Folk or Longbeards. The first of these rulers were inhabitants of Khazad-dûm long descended from Durin. They ruled and lived there for thousands of years until TA 1980 when miners awoke a Balrog which eventually drove out the Dwarves. Afterwards, its successors lived elsewhere and founded other kingdoms such as places like Lonely Mountain (Erebor), the Grey Mountains (Ered Mithrin), and the Blue Mountains (Ered Luin).