Though the One Ring originally appeared in Tolkien's children's fantasy novel The Hobbit in 1937, all twenty Rings of Power are mentioned in The Lord of the Rings, which primarily focuses on the assembly of the Fellowship from all of the races of Middle-earth to aid Frodo in finally destroying the One Ring by returning it to Mount Doom. According to Tolkien, the purpose of the Rings was to give their respective wearers wealth and dominion over others, though the Three were specifically made to heal and preserve Elvendom in Middle-earth. This power appealed most to the Elves, whose gift of immortality made them desire to keep the physical world of Middle-earth unchanged and to delay the inevitable Dominion of Men. Tolkien's subsequent posthumous works, including The Silmarillion, Unfinished Tales, and The History of Middle-earth, give more detailed accounts of the history of the Rings of Power.