Dwarves of the Grey Mountains
The Dwarves of the Grey Mountains were the Dwarves of Durin's folk who lived in the Grey Mountains in northern Middle-earth. They fled to the Grey Mountains in Third Age 1981 after a Balrog was unearthed in their ancestral home of Khazad-dûm. Another portion of their clan established the kingdom of Lonely Mountain, but King Thorin I, learning that most of his people remained in the Grey Mountains, abandoned Lonely Mountain to join the Dwarves to the north.
Increasing attacks by Dragons plagued the Dwarves until King Dáin I was slain by a Cold-drake in 2589. Durin's folk then left the Grey Mountains, with some returning to Lonely Mountain while others founded their own kingdom in the Iron Hills.
It is possible that the Dwarves returned to the Ered Mithrin and retook their halls from the Dragons and Orcs that dwelt there.