Eru Ilúvatar
The Tolkien scholar Charles W. Nelson described Gollum as an evil guide, contrasted with Gandalf, the good guide (like Virgil in Dante's "Inferno") in "Lord of the Rings". He notes, too, that both Gollum and Gandalf are servants of The One, Eru Ilúvatar, in the struggle against the forces of darkness, and "ironically" all of them, good and bad, are necessary to the success of the quest.