Seeking to conquer all of Middle-earth, Sauron created the One Ring in order to control all the other rings. However, the creation of the Ring caused many races to go to war. There on the Last Alliance of Men and Elves, theh Ring transf
erred its loyalty to Isildur after he avenged his father's death and after Sauron was (partially) defeated. Later, the ring betrayed Isildur and then was found byt he creature Gollum, whose mind was twisted by it. The Rign was later lost by Gollum
In Peter jackson's film series Edit
The Lord of the Rings and The Hobbit
The One Ring's role stays the same in the film, but has an angrier influence on Frodo than the other adaptations.