Gollum was once a Hobbit-like creature named Sméagol. For years and years now, his body and soul have been poisoned by the power of a small, plain, gold ring that he has kept hidden deep in a dark cavern within the Misty Mountains. Gollum does not know about the true nature this Ring. He only knows it is more “precious” to him than life itself. After a chance meeting with an intruder in his caves, Gollum discovers he has lost his “precious”! He suspects, quite rightly, that it is now in the hands of one Bilbo Baggins, a Hobbit of the Shire. And so begins a pursuit that will cross mountains and wastelands, span years and cost many lives until at last, this wretched creature will hold the very fate of Middle-earth in his hand.
See Gollum in 79000 Riddles for The Ring