"One for the Dark Lord on his dark throne; One Ring to rule them all...One Ring to find them...One Ring to bring them all and in the darkness bind them."

The One Ring, secretly forged by Sauron in the heart of Mount Doom, had the power to dominate the other nineteen Great Rings. Sauron's intent was to command the minds of the other ring bearers through their rings of power. His original intention was for the Rings to be given to Elves of power and influence. Sauron then intended to forge the One Ring which, through the lesser rings, would allow Sauron direct influence over the thoughts of the other ring-bearers. Had it succeeded perfectly, Sauron would have achieved dominance over the Elves with no military action required. However, for this plan to be successful the Ruling Ring would have to be significantly stronger than the other rings, and Sauron put a great amount of his own power into the Ring in order to achieve this. As the Ruling Ring, it had all the powers of the other rings, but to a far greater extent, and had some powers uniquely its own. While Sauron's plan didn't succeed perfectly, the existence of the One Ring on his finger meant that the other rings, with which many kingdoms had been built, could not be used safely. Additionally, intentionally or not, Sauron's personal power was greatly enhanced so long as he wore the Ring, giving him military might the likes of which he could never have otherwise achieved.

Unlike the other great rings, the One Ring held no gem and had no intricate designs on it, at least at first glance. To an ordinary layman it would appear as a simple golden band. Heating the Ring in even a small fire, however, would reveal part of Sauron's incantation in an Elvish script written along the Ring. According to Isildur, Sauron's hand was "black and yet burned like fire." (The Fellowship of the Ring) He also references how the script was visible on the Ring while Sauron wore it. It was virtually indestructible, and no craft or power possessed by the Elves or Gandalf could harm it in any way. It also appeared to have a will of its own (or at least, the ability to independently carry out Sauron's will since it contained a large portion of his being), and could expand or shrink by itself in order for different races to wear it.

It was Isildur who cut the Ring off Sauron's hand. He had the chance to destroy the One in the very chambers where it was forged, but was corrupted by the Ring, and spared it. Later it betrayed him, resulting in his death. It was found, 2500 years later, by a Stoor named Déagol. Déagol was then killed by his cousin, Smèagol (later Gollum), who then took the Ring for himself. Smèagol was quickly corrupted, but had a strong physical resistance to the Ring, and "for 500 years the Ring poisoned his mind." Later, a Hobbit, Bilbo Baggins found Smèagol living under the Misty Mountains. Bilbo got the Ring by chance, and at the end of all his adventures he still had it. Later the One was passed down to Frodo Baggins, who was forced to flee to Rivendell, chased by the Nazgûl. He was chosen there to take the chance Isildur threw away: to destroy the One in the fires of Mount Doom. Upon finding Frodo (as he believed) dead, Samwise Gamgee took the Ring to protect it. After discovering Frodo alive, Sam returned the Ring. Frodo, after a long and difficult journey, ultimately failed in his effort to destroy the One Ring. In the Sammath Naur, the place where its power was strongest, the Ring corrupted Frodo, and he tried to take it to keep for himself. Sméagol came up behind him, bit off his finger and the Ring, and fell off the edge into the lava below. The One Ring was destroyed, and Sauron defeated.

"Three rings for the Elven kings under the sky..."

Celebrimbor forged the Three Rings by himself, and they were never touched by Sauron. They were called Narya (the Ring of Fire), Nenya (the Ring of Adamant), and Vilya (the Ring of Air). Narya was first worn first by Gil-galad, who gave it Círdan, and was lastly worn by Gandalf. Gil-galad also initially owned Vilya, before Elrond inherited it after the former's death. Nenya was worn only by Galadriel.

They remained hidden, and the whereabouts of the three were not openly revealed until the end of the Third Age, after the One Ring was destroyed, and the Dark Lord Sauron was overthrown. Instead of making the wearer invisible, these rings were themselves invisible. Galadriel revealed her possession of one of the rings to Frodo Baggins while he was in Lothlórien, after his possession of the One Ring enabled him to see her ring. Later, while traveling down the River Anduin, Frodo spoke of it to Aragorn, who admonished him not to speak of it outside of Lórien.

Each of the Three Rings had special properties, but their powers were limited. During the Council of Elrond, Elrond stated that neither Rivendell, nor Lórien, nor the Grey Havens (the locations of the Three Elven Rings) had the power to withstand the might of Mordor.

"Seven for the Dwarf-lords in their halls of stone..."

Sauron presented the Seven Rings to the Dwarf-lords. This might have been the division of seven Dwarf clans mentioned in The History of Middle-earth: Durin's Folk, Firebeards, Broadbeams, Ironfists, Stiffbeards, Blacklocks, and Stonefoots.

The Dwarves used their Rings to establish their fabled treasure hoards (which in turn attracted dragons), but Sauron, according to portions of The Silmarillion, was unable to force the Dwarven bearers to submit to his will. Indeed, the rings did not even turn them invisible; and the Dwarves were immune to some of the rings' more detrimental effects. It is believed that the Dwarves' natural hardiness, and the fact that it was only the more powerful Dwarf lords who possessed them, made them resistant to Sauron's control. While it is not directly stated, the Rings possibly gave the Dwarf lords who wielded them an increased life span. The net effect of these rings was to bring vast wealth to the wearer and but to also intensify their greed, which ultimately led to the wielders' ruin. At the time of the War of the Ring four rings had been consumed by dragon fire and the rest re-acquired by Sauron.

"Nine for mortal men doomed to die..."

The nine rings for mortal men were those divided amongst those men doomed to become the Nazgûl, the Ringwraiths. These ring-bearers held rings that were controlled by Sauron, for they became evil servants of his. None are mentioned specifically throughout The Lord of the Rings save their leader, the Witch-king of Angmar. His second-in-command was named in the Unfinished Tales as Khamûl, the Black Easterling.

The line from Tolkien's epigraph, "Nine for Mortal Men doomed to die" refers to the fate of men, uniquely among the creations of Eru to pass beyond Arda to a destiny unknown to the Elves. It was this uncertainty, and Men's envy of Elven immortality in the Blessed Realm, which Sauron exploited, leading to the destruction of Númenor. The effects of the Nine on the Men were that they each acquired great power and wealth, became powerful Sorcerers and appeared to have eternal life, for they did not age. After a time however, life became unendurable to them, and when they put the Rings on, they often beheld the phantoms and delusions of Sauron. One by one, according to the nature of the Man and his innate inability to resist evil, they fell under Sauron's permanent control, and became wraiths who did only Sauron's bidding. They remained permanently invisible, except to those Elves who had once dwelt in the Undying Lands (few indeed by the Third Age) and Maiar such as Sauron and the Wizards. They were also visible to whomever wore the Ruling Ring (whether the other Rings conferred this ability is unknown). This process also appeared to link their lives and power with Sauron's, making them little more than extensions of his will. When Sauron's power was weak, the wraiths themselves were also fairly powerless. As Sauron became stronger however, they became much more powerful, to the point where the Witch-king was presumably able to match Gandalf the White in strength. It is unclear where the Nine were physically kept. At the Council of Elrond the history of the Rings of Power is discussed, and it is stated that Sauron has "gathered the Nine to himself," although it is also said that "the Nine the Nazgûl keep." This could mean either that the Nazgûl wear their rings while in the service of Sauron, or it could mean that after they fell and became enslaved to his will Sauron took their rings and kept them in Barad-dûr as he did with the remaining Dwarf rings and set the Nazgûl to guard them. There is no mention of any of the Nine when the Nazgûl are seen, and most notably when the Witch-king was slain Tolkien does not describe him wearing a ring, nor did either Gandalf or Aragorn express concern about what happened to the ring afterwards. This implies that at the very least the Nazgûl don't wear their rings constantly, although they may sometimes put them on still.

"Build me an army, worthy of Mordor..." - Sauron

The palantíri (sometimes translated as "Seeing Stones") were stones that could be used in communication with one another, and also to see many things across the face of the world. When its master looked in it, he could communicate with other Stones and anyone who might be looking into them; people of great power can manipulate the Stones to see virtually any part of the world.

"They found The Arkenstone, the heart of the Mountain..." - Balin

The Arkenstone or Heart of the Mountain was a wondrous gem sought by Thorin Oakenshield which had been discovered beneath the Lonely Mountain during the reign of Thráin I, and then shaped by the Dwarves. The Arkenstone became the family heirloom of the Kings of Durin's Folk, but was lost when the dragon Smaug stole the mountain from the Dwarves.

The Arkenstone shone of its own inner light, and appeared a "little globe of pallid light" in darkness, and yet, cut and fashioned by the Dwarves, it took all light that fell upon it and changed it into "ten thousand sparks of white radiance, shot with glints of the rainbow".

"Saruman, your staff is broken." - Gandalf the White breaking Saruman's staff

A Wizard's staff (pl. staves) was the primary tool, power conduit, and sometimes weapon of the Istari (or, the Order of Wizards), which might have also served as a symbol of their power or rank. Since there were a total of five Istari in the Order of Wizards, there were only five wizard staves.