De um FAQ sobre os Anéis :
Was Sauron visible when wearing the Ring?
Though Tolkien never answered this question directly, most opinion in r.a.b.t is that Sauron was visible even while wearing the Ring.
The Rings of Power (except the Three) made their wearers invisible by shifting them mostly into the Unseen world. But Sauron already lived in that world as a Maia (an “angelic” spirit).
His material body was something deliberately put on, as we put on clothes. Sauron was naturally pure spirit, not a hybrid like mortals, Elves, and Dwarves.
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Então, existem basicamente dois mundos, o material e o mundo espiritual . Colocar o Anel muda um em parte para o mundo espiritual. Mas Sauron já vivia no mundo espiritual .