Ring of Thrór
The first of the Seven Dwarf-rings to be forged, and the last to be recovered by Sauron. It was originally given to King Durin III of Khazad-dûm by the Elves of Eregion, and it remained in his line for thousands of years until it was inherited by Thrór, the King under the Mountain at Erebor. It was during Thrór's reign that Smaug descended on Erebor and drove the Dwarves into exile. Long after Erebor's destruction, Thrór passed the Ring to his son Thráin, who dwelt for many years as an exile from his ancient home. At last, Thráin set out on his own ill-fated Quest of Erebor, but he was captured by the spies of Sauron, and the Ring of Thrór was lost.