AnnatarAnnatar - After the founding of Eregion by the Elves near the Misty Mountains, Sauron became concerned by their encroachment on the land he sought to dominate.  So he moved against them, not in power, but rather by deceit.  He took upon himself the form of a "being of light".

 

"...long he sought to persuade the Elves to his service, for he knew that the Firstborn had the greater power; and he went far and wide among them, and his hue was still that of one both fair and wise...for Sauron took to himself the name of Annatar, the Lord of Gifts." ~The Simarillion (Of the Rings of Power and the Third Age)

 

His deception proved successful; he feigned friendship with the Elves of Eregion, passing knowledge on to them, but at the same time, learning much of smithing skills, which would prove disastrous in the age to come.

 

"...he told of the Elven-smiths of Eregion and their friendship with Moria, and their eagerness for knowledge, by which Sauron ensnared them.  For in that time he was not yet evil to behold, and they received his aid and grew mighty in craft, whereas he learned all their secrets..." ~The Fellowship of the Ring, Book II, chap. 2 (The Council of Elrond)