Nazgûl

The nine Nazgûl were the most feared minions of Sauron. They are wraithes given visible form only the the clothes they wear. They chase Frodo in an attempt to retrieve the One Ring from him. Later they fought against the armies of men at the Black Gate of Mordor. They used to be kings of men but they were enslaved by the the power of the One Ring. They were destroyed when Sauron was killed.