In The Lord of the Rings, Gollum bites the One Ring from Frodo’s finger.
At the Cracks of Doom, Frodo claims the Ring instead of destroying it. Gollum attacks him, bites off his finger, and falls into the volcanic fire while clutching the Ring. This accidental struggle causes the Ring’s destruction and ends Sauron’s power.
Gollum was once Sméagol, a river hobbit-like figure who found the Ring long before the events of the main story. Its influence isolated and transformed him, and he eventually became the creature known as Gollum. His obsession makes him both an antagonist and an essential, unwilling agent in the quest’s success.
A common simplification says Frodo destroyed the Ring. Frodo carried it to the place of destruction, but he did not willingly cast it into the fire. The final physical act was caused by Gollum’s bite and fall.