The One Ring was one of the most powerful artifacts ever created in Middle-earth. It was crafted by the Dark Lord Sauron in the fire of Orodruin, also known as Mount Doom during the Second Age.
Sauron’s intent was to enhance his own power, and to exercise control over the other Rings of Power, which had been made by Celebrimbor and his people with Sauron’s assistance. In this way, he hoped to gain lordship over the Elves and all of the other races in Middle-earth.
To accomplish this goal, Sauron knew that the One Ring would need to contain an extraordinary amount of power. As such, he concentrated within the Ring a great part of his own fëa (soul). In this way, Sauron’s fate became bound to that of the One Ring. If it were damaged or destroyed, so too would be Sauron’s strength and power.
The One Ring was also known as the Ruling Ring, the Master Ring, the Ring of Power, and Isildur’s Bane.