The Nazgûl, or Ringwraiths in the Common Speech, were some of the most memorable antagonists in The Lord of the Rings. As explained in both J. R. R. Tolkien's novel and Peter Jackson's film adaptations, Sauron gave nine magical rings to the race of Men. These Rings of Power corrupted their wearers, thus bending them to Sauron's will and transforming them into invisible, undead monsters. Despite their importance in the story, neither the novel nor the films offered much information about who the Nazgûl used to be.
Source：https://www.cbr.com/lord-of-the-rings-nazgul-explained/
