Once great kings of Men, the Nazgul were corrupted by the magic rings given to them by Sauron the Dark Lord. They bacame formless creatures, frightening specters, slaves to the will of the Dark Lord who sent them out as agents of his will to scour the lands of Middle-earth for the One Ring. To most they appeared as black-robed figures on horseback, projecting about themselves an overwhelming aura of fear. Frodo, hovever, saw the Ringwraiths in their true form when he placed the One Ring on his finger at Weathertop. They appeared to him as wretched husks of their former selves, tall and thin, drawn and sapped of their mortality till all that remained were pale, twisted masks of the will of Sauron.