The underground realm ruled by Durin’s Folk in J.R.R. Tolkien’s Middle-earth is Khazad-dûm.
Khazad-dûm is the Dwarves’ original name for the vast subterranean city and kingdom beneath the Misty Mountains. It becomes famous for its mines of mithril, a remarkably valuable and light metal. The Dwarves’ wealth and excavation eventually awaken a Balrog, after which the kingdom is abandoned and the place becomes known in the Common Tongue as Moria.
In The Lord of the Rings, the Fellowship travels through the deserted halls of Moria. The name Moria is therefore not a separate neighboring kingdom but the later name associated with the ruined realm. Khazad-dûm is also connected with Durin the Deathless, the first king of Durin’s Folk. Readers sometimes confuse it with Erebor, the Lonely Mountain, another important Dwarven stronghold.