The powerful Maia who becomes Sauron in J.R.R. Tolkien’s legendarium was originally named Mairon.
Mairon was a Maia associated with the Vala Aulë before he was corrupted by Melkor, later called Morgoth. After joining Morgoth, he became known as Sauron, a name associated with his role as a terrible servant and later rival of his former master. His ambition shifts from serving another power to imposing his own order over Middle-earth.
Sauron’s history spans the First, Second, and Third Ages. In the Second Age, he helps create the Rings of Power and secretly forges the One Ring in Mount Doom. Tolkien’s texts also use other names for him, including Annatar and Gorthaur. Mairon should not be confused with Olórin, the Maia who becomes Gandalf, or Curumo, the Maia who becomes Saruman.