Sauron (pronounced [ˈsaʊrɔn]) is the title character and the primary antagonist, through the forging of the One Ring, of J. R. R. Tolkien's The Lord of the Rings, where he rules the land of Mordor and has the ambition of ruling the whole of Middle-earth. In the same work, he is identified as the "Necromancer" of Tolkien's earlier novel The Hobbit. The Silmarillion describes him as the chief lieutenant of the first Dark Lord, Morgoth. Tolkien noted that the Ainur, the "angelic" powers of his constructed myth, "were capable of many degrees of error and failing", but by far the worst was "the absolute Satanic rebellion and evil of Morgoth and his satellite Sauron". Sauron appears most often as "the Eye", as if disembodied.
Tolkien, while denying that absolute evil could exist, stated that Sauron came as near to a wholly evil will as was possible. Commentators have compared Sauron to the title character of Bram Stoker's 1897 novel Dracula, and to Balor of the Evil Eye in Irish mythology. Sauron is briefly seen in a humanoid form in Peter Jackson's film trilogy, which otherwise shows him as a disembodied, flaming Eye.
Source : Wikipedia