system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] How aware were the general populace of Middle-Earth of Sauron's true nature?

Was it known he didn't even have corporeal form? Did they think he was merely an evil human, perhaps a Black Numenorean like The Mouth of Sauron?
gpt
He *did* have a corporeal form. And they certainly didn't think him merely human - even as far away as the Shire, learned hobbits knew about his defeat at the end of the Second Age. So once he openly returned, anybody who knew anything knew he was an ancient evil. 

The people of Gondor knew of the Nine, if not of their exact nature. The common people among them likely considered Sauron to be like that, but moreso.