One Ring

The One Ring was an item of evil owned by Sauron.

History
After the Elves created the Rings of Power, Sauron returned to Mordor and in the fires of Mount Doom he forged the One Ring. He put most of his power into it, hoping to control the other rings, and thus all Middle-earth. When he wore the Ring, the Elves realized what Sauron truly were and removed their Rings of Power.

When Numenor was destroyed, Sauron was destroyed as well, but his spirit survived as his power was contained in the One Ring.

Then Isildur cut it from his finger with Narsil, during the last battle of the Second Age and it broke. Elrond adviced him to throw it in Mount Doom and end the existence of Sauron, but Isildur refused, keeping it as a trophy to avenge his father Elendil.

In the beginning of the Third Age, Isildur was ambushed by Orcs as he crossed the Great River on his way to Arnor. The Ring fell from his finger as he swam and exposed him to Orcs archers.

Orcs fought against the forces of Gondor as Sauron was looking for his One Ring. It was found by two Hobbits. Deagol showed it to his friend Smeagol who murdered Deagol and took the Ring as his own. He was driven ot and Gollum which he called it "Precious" fled into a cave in the Misty Mountains. It was won by the Hobbit Bilbo Baggins in a contest of riddles. Bilbo used to it to make himself invisible but he became very attached and when Gandalf urged him to leave it to his nephew, he was hesitant. When he left the Shire, he gave it to Frodo Baggins.

Properties
The Ring is a burden to anyone who carries it. It has the ability to render anyone who wears it invisible, to dominate those who wear the lesser Rings of Power and to preserve their life, though, as Gandalf has said, this is really an Unlife, where one eventually becomes a wraith and falls under the will of Sauron.

The Ring is known to have a mind of its own, and manipulates its owner trying to escape and come back to its Master.

The Ring drains the Will of anyone who uses it, until it's reduced to Zero, they are effectively dead. It is used mostly by hobbit characters.