- "Seven for the Dwarf-lords in their halls of stone."
- —J.R.R. Tolkien
The Ring of Thrór was the mightiest of the seven Dwarven rings.
While Sauron himself gave the Dwarves their Rings of Power, this one was originally given to King Durin III of Khazad-dûm by Celebrimbor, and it remained in his line for thousands of years until it was inherited by Thrór, the King under the Mountain.
It was during Thrór's reign that Smaug descended on Lonely Mountain and drove the Dwarves into exile. Long after his kingdom'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 an ill-fated quest to regain his kingdom, but he was captured by the spies of Sauron, and the Ring of Thrór was lost forever.
Many Dwarves however did not know the fate of the Ring, and thought that it was lost in Moria when Thrór was killed by Azog. It was thought that one of the reasons Balin wished to reclaim Moria was to find the Ring. In the Council of Elrond, Gandalf told Glóin that Balin would not find the Ring there, as it was given to Thráin and lost in Dol Guldur.
Portrayal in adaptations
The Hobbit film trilogy
In the extended edition of The Hobbit: An Unexpected Journey, Gandalf expresses concern about the fate of this ring, identifying it as the last ring of the Seven not said to be in Sauron's power when he fell, with four destroyed and two taken by Sauron. In the extended edition of The Hobbit: The Desolation of Smaug, when Gandalf discovers Thrain in Dol Guldur, a flashback confirms that Thrain possessed one of the Seven during the attempt to retake Moria, with Azog having cut off the top of Thrain's left index finger to take his ring.