One Ring

The One ring is a magical item featured in The Hobbit. It first appears in the first film and the rest of the series. Prior to the series, it was created by Sauron to take over all species and races of Middle-earth. However, Isildur stole it while defeating the evil wizard. It later fell into the possession of Gollum after he killed his cousin. Bilbo later stole the Ring and used it to make himself invisible ever since.