Sauron, one of Morgoth’s followers, is the greatest villain in the world; The Lord of the Rings saw him finally defeated, but not totally without hope of return. Written by the father of modern fantasy, this book was published in three parts between 1954 and 1955. J. R. R. Tolkien’s masterwork was expertly adapted into Peter Jackson’s Lord of the Rings movies, which tackled one part of the book per movie. Sauron’s reign of terror also came crashing to a halt at the end of Jackson’s final Lord of the Rings movie, but one prophecy may have enabled a comeback.

https://screenrant.com/lord-of-the-rings-sauron-return-dagor-dagorath-explained/