Most readers of The Lord of the Rings book trilogy and fans of Peter Jackson's Lord of the Rings film trilogy are familiar with the Nazgûl (also know as ringwraiths or the Úlairi). They are servants of Sauron, dark and cloaked figures, and are often found astride black horses or felbeasts. But where do they come from? The answer to this question reaches deep into the history of Middle Earth, but also may provide clues as to what viewers can expect in Amazon's upcoming and much-anticipated Lord of the Rings series.