Annatar was a fair form used by Sauron to deceive Celebrimbor and the Elves of Eregion. After lying hidden and dormant for about 1000 years, Sauron put on a fair visage in the Second Age, and calling himself Annatar, the Lord of Gifts, he befriended the Elvish smiths of Eregion, and counseled them in arts and magic.
Portrayal in adaptations
At an early stage of script development and shooting, Annatar was to be featured in Peter Jackson's The Return of the King. The fair form of Sauron would appear when Aragorn called him forth. After blinding everyone, he would change into the black armoured Sauron that appeared in the rest of the film, and battle Aragorn. This idea was scrapped, but footage still exists.