The One Ring links The Hobbit and J.R.R. Tolkien’s The Lord of the Rings.
Bilbo Baggins finds the Ring during the underground riddle contest with Gollum in The Hobbit. At first, the object appears to be a powerful invisibility ring. In The Lord of the Rings, Tolkien develops its identity and purpose: it is the One Ring created by Sauron to control the other Rings of Power.
The Ring’s role was revised between early editions of The Hobbit and the later mythology. Tolkien’s original version treated Bilbo’s acquisition as a more ordinary discovery, but later revisions made the account fit the darker history revealed in The Lord of the Rings. This is why different editions can contain changes to the chapter “Riddles in the Dark.”
The One Ring should not be confused with the Arkenstone, which belongs to the quest in The Hobbit, or the Silmarils, which are central to The Silmarillion. Sting is Bilbo’s sword, later carried by Frodo, not a ring.