King under the Mountain
Title given to the kings of Erebor by the founder of the dwarven kingdom, Thráin I. Thráin I's son, Thorin I, and four of his descendants (Glóin King of Durins Folk, Óin King of Durins Folk, Náin II, and Dáin I) ruled from the GreyMountains and did not have the title. Thrór returned the kingship to Erebor and took up the title until Smaug took it himself after he ransacked the LonelyMountain. Thorin II returned the title and kingship after the destruction of Smaug. After Thorin's death, Dáin II took over the kingship and the title and the title was passed down to his soon Thorin III.