The Dark Wizard Annatar in the land of Mordor

"After a thousand years, Sauron had taken control of a land of his own, which became known as Mordor, and had begun to bring the peoples of Middle-earth under his power. He found it a simple matter to sway Men to his allegiance, but the Elves proved more difficult to influence, and so Sauron devised other means to place them under his control.

Sauron's scheme to entrap the Elves was one of subtle persuasion. He took on the angelic appearance of an emissary of the Valar and gave himself new names. Among these were Artano the high smith and Aulendil the servant of Aulë, but the best known of these guises was Annatar, the Lord of Gifts. In this form he went to the Elves and offered them his aid in their works, but even as Annatar most of the leaders of the Elves were suspicious of him. He was rebuffed by Gil-galad, Elrond and Galadriel, but the Jewel-smiths of Eregion were less suspicious, and their leader Celebrimbor accepted his offers of knowledge and help."