[HerenIstarion]

The One Ring came to life only because Bilbo of the Hobbits came upon wonderful magic ring which made it's bearer invisible. When JRRT started to write a sequel of very succesful book upon the request of a publisher, he found himself unable not to connect the whole hobbitish world to the main stream of his writings - Middle Earth, and this connection came through the ring found by Bilbo - which was made to be greatest of many similar rings, yet only One to be their master.

And if any needs to have a symbolism in the matter of rings, one can consider it as a symbol of technology ill used, which leads to the victory over the nature, yet helps not to comprehend it or live in harmony with it, which helps the user to obtain power, yet corrupts him through it, for power may become source of the greatest of sins - pride.