"Now Sauron's lust and pride increased, until he knew no bounds, and he determined to make himself master of all things in Middle-earth, and to destroy the Elves, and to compass if he might, the downfall of Númenor. He brooked no freedom nor any rivalry, and he named himself Lord of the Earth. A mask he still could wear so that if he wished he might deceive the eyes of Men, seeming to them wise and fair. But he ruled rather by force and fear, if they might avail; and those who perceived his shadow spreading over the world called him the Dark Lord and named him the Enemy; and he gathered under his government all the evil things of the days of Morgoth that remained on earth or beneath it; and the Orcs were at his command and multiplied like flies."
Sauron (Quenya; [ˈsaʊron] or [ˈθaʊron]), the eponymous Lord of the Rings, was the greatest subversive Maia, maker of the One Ring, renowned disciple of Aulë, and chief agent of Morgoth in the Elder Days. After Morgoth's ousting by the Valar, Sauron became the second Dark Lord and sought to conquer most of Arda through guileful trickery, with the Rings of Power or with overwhelming armies.

At the end of the Second Age, Sauron caused the Downfall of Númenor, and was then defeated in Mordor in the War of the Last Alliance of Elves and Men united under Gil-galad and Elendil. In the final battle, Isildur managed to cut the One Ring from his hand, dismantling his corporeal form and robbing him of much of his power. After centuries lying dormant, rebuilding strength and stirring awake evil things, Sauron returned to power late in the Third Age and strove to dominate Middle-earth. In the end he was vanquished at the destruction of his Ring in Mount Doom.