Sauron should be thought of as very terrible. The form that he took was
that of a man of more than human stature, but not gigantic.
In his earlier incarnation he was able to veil his power
(as Gandalf did) and could appear as a commanding
figure of great strength of body and supremely
royal demeanour and countenance.
(Letters, № 246)
Readers of The Lord of the Rings are well aware of Sauron’s being the chief menace of the Second and Third Ages after the capture of Morgoth and the War of Wrath. What is rather obscure, though, is what the great Middle-earth adversary looked like. In his writings and letters Tolkien gave a few clues concerning the looks of Sauron, leaving all the rest to his readers’ imagination.