The Witch-King was once a man, but became the Lord of the Nazgûl and Sauron’s most dreadful servant after being corrupted by one of the Nine Rings of Power. It is presumed that the nine Nazgûl, of whom the Witch-King was one, were the Lords of the Númenorean race and it was to these that Sauron gave the Nine Rings of Power in the 1600’s of the Second Age, after he had seized the Rings from Eregion.
The Witch-King was the tallest of the Nazgûl and wore a crown. His power was the greatest and he was the most feared, only being able to be harmed by blades touched by special spells, ordinary blades perishing when they touched him.
In TA 1300, the Nazgûl arose. Their Lord took the name Witch-king, formed the Realm of Angmar, and set out to defeat the weakened Dúnedain of Arnor. He then led wars against the North-kingdom until TA 1975. After defeating Arthedain, he was put to flight by armies led by Círdan, together with Glorfindel, and Eärnur of Gondor in the Battle of Fornost. It was then Glorfindel who counselled Eärnur not to pursue him, saying:
“Far off yet is his doom, and not by the hand of man will he fall.”
The Witch-King then disappeared from the North, but later, attacked and besieged Minas Ithil, renaming it Minas Morgul and naming himself it’s Lord. In TA 2050, the Witch-King challenged Eärnur, King of Gondor to single combat, resenting the fact that he had not been able to face Eärnur at the Battle of Fornost. Sadly Eärnur was slain.
During the War of the Ring, the Witch-King led the Ringwraiths in the hunt for the One Ring and Frodo Baggins, wounding the Hobbit at Weathertop. Commanding the army which attacked Minas Tirith during the Siege of Gondor, he was prevented from entering the City by Gandalf and by the timely intervention of the Rohirrim. He then turned his attention to the battle field and mounted a Fell Beast, descended his foes wielding a black mace, bringing despair. He found Théoden King of Rohan and pierced the King’s horse, Snowmane with a black dart, causing the horse to fall and crush Théoden beneath him. It was then that the Witch-King met his death – caused, as we know, not by the hand of a man.