Most ancient and famous of all the Dwarven kingdoms was Khazad-dûm, the ancestral home of Durin the Deathless, the first of the Seven Fathers of the Dwarves. Through five Ages of the Stars and three Ages of the Sun, these were the dwarves who had a long friendship with the Elven-smiths of Eregion (who forged the Rings of Power). But in the accursed years of Sauron's dominion of the Second Age of the Sun , the Dwarves closed their great doors to the World. At that time, the great mansions of Khazad-dûm were renamed Moria, the 'black pit' or 'dark chasm'.
Yet still the dwarves worked and quarried the forges beneath the Misty Mountains until TA 1980 of the Third Age. In that year, they delved too deeply beneath Mount Barazinbar and a Balrog was unleashed on the halls of Moria and slew their king, Durin VI. This creature of darkness was henceforth called Durin's Bane by the Dwarves. So terrible was the Balrog's strength that all were either slain or driven from their kingdom. When the Fellowship of the Ring entered Moria, it had been long-abandoned by the Dwarves, stripped by the Goblins, and through the barren corridors and halls still stalked Durin's Bane, who was feared even by the roving bands of Goblins and Mountain Trolls .

After many centuries, Thrór, a decendent of Durin, went to Moria to see its splendors for himself. Unfortunately, like most of the underground parts of the Misty Mountains, the place was infested with Goblins. Their leader, Azog, slew Thrór and sparked the long War between Dwarves and Orcs . Though Azog was eventually defeated, Durin's Bane had not left the place, and the Dwarves could not return there.

Later, Balin son of Fundin attempted to colonize the place, but a combination of Goblins and the Balrog soon ended the ill-fated attempt.