Sauron are a genetically engineered variation of humans, created during the darkest parts of the Gene Wars. They were designed to manufacture deadly diseases, as walking biological weapons factories. They were responsible for millions, possibly billions, of deaths.
Hated and reviled, they were typically executed on sight if discovered. Even after the wars ended, they were universally denied any form of basic human rights.
Few survived the wars and subsequent retaliatory purges. Those who did were ultimately exiled to the prison colony world dubbed New Mordor, where a blockade of starships has maintained strict quarantine of the entire planet ever since.