Nazgûl

"They were once Men. Great kings of Men. Then Sauron the Deceiver gave to them nine rings of power. Blinded by their greed, they took them without question, one by one falling into darkness. Now they are slaves to his will. They are the Nazgul, Ringwraiths, neither living nor dead. At all times they feel the presence of the Ring, drawn to the power of the One. They will never stop hunting you."

- Aragorn to the Hobbits on the Nazgûl

The Nazgûl are supporting antagonists in The Lord of the Rings series, as well as the series' prequel series, The Hobbit.

History
The Nazgul were once great kings. One day, Sauron the deciever gives each of them a ring. one by one, they became Sauron's servants. When their king died, they were all buried in the same tomb. However, they were all resurrected by Sauron's evil magic. They were also defeated by Galadriel and later defeated by Frodo Baggins and Sam Gamgee ruining the One Ring.