Of course, as readers of the Silmarillion we all know how pivotal of a figure he will eventually be, and are presented with all of these isolated incidents of his existence in the Silmarillion and histories as clearly marked narrative events. We know that Thu is Sauron, that Mairon is Sauron, that the Necromancer and Annatar and Zigur are all different names and faces for the same perceptive bit of fire. But those that experience those thousands and thousands of years of history, they don't. Sauron was not just not a household name, he as a concept did not exist. The people of first age Beleriand knew of ten dozen insidious servants of Morgoth, spirits of malice, influences on their lives. They knew of the terrible sorcerer who terrorized the lands with his vicious wolves. They knew of the dread regent who once kept rule in Angband as it rotted beneath the ground, waiting for Melkor to return. They know of the fiery soldier they saw in the battle under stars, decimating their troops before they had barely set foot on mortal soil. They knew of the trickster spirit who took the forms of their dead loved ones, played out the facade for far longer than necessary to extract any amount of ransom. They knew, vaguely, of an old tale of Aule's greatest Maia, gone wayward and disappeared with the Dark Lord. Some escaping Angband might know of a certain beautiful man who attends the lord's side, lithe and lovely, or a torturer of Maedhros, purveyor of many cruel experiments. But rarely, if ever, were even two of these faces correlated. There were many forms of evil, to them, and only so many of these small evils could possibly survive after his death.
To learn, for the elves when he finally put that damn ring on for the first time, that not only have you been fooled once, that your lovely Annatar was a servant of Morgoth, but that he was all of them.
All this time, after thousands of years, it was a one man play, and the name beneath every single role was the same ungodly dedicated freak of a man, and you are all FUCKED IN THE ASS.