The Lord of the Nazgûl, also called the Witch-king of Angmar, the Pale King, or Black Captain, is a fictional character in J. R. R. Tolkien's fantasy novel The Lord of the Rings. He was one of the Nine among Men that the dark lord Sauron gave Rings of Power, becoming Nazgûl or Ringwraiths. His ring gives him great power, but enslaves him to Sauron and makes him invisible. As a wraith, he had once established himself King of Angmar in the north of Eriador. In the events of the Lord of the Rings, he stabs the bearer of the One Ring, the Hobbit Frodo Baggins, with a Morgul-knife which would reduce its victim to a wraith. Much later, in his final battle, the Lord of the Nazgûl attacks Éowyn with a mace. The Hobbit Merry Brandybuck stabs him with an ancient enchanted Númenórean blade, allowing Éowyn to kill him with her sword.

In early drafts, Tolkien had called him the "Wizard King", and considered making him either a renegade member of the Istari, or an immortal Maia, before settling on having him as a mortal Man, corrupted by a Ring of Power given to him by Sauron. Commentators have written that the Lord of the Nazgûl functions at the level of myth when, his own name forgotten, he calls himself Death and bursts the gates of Minas Tirith with magical spells. At a theological level, he embodies a vision of evil similar to Karl Barth's description of evil as das Nichtige, an active and powerful force that turns out to be empty. The prophecy that the Lord of the Nazgûl would not die by the hand of Man echoes that made of the title character in William Shakespeare's Macbeth.

The Witch-king first appears in the Second Age of Middle-earth. The Dark Lord Sauron gave Rings of Power to powerful Men, including kings of countries in Middle-earth. These confer magical power, but also enslave their wearers to the owner of the One Ring, Sauron himself.

The Lord of the Nazgûl appears as the Witch-king of Angmar during the Third Age and is instrumental in the destruction of the Northern kingdom of Arnor. In his notes for translators, Tolkien suggested that the Witch-king of Angmar, ruler of a Northern kingdom with its capital at Carn Dûm, was of Númenórean origin. Nothing is heard of him when Sauron is overthrown by the Last Alliance of Elves and Men late in the Second Age, but his survival is assured by the power of the One Ring.

Over a thousand years later in the Third Age, the Lord of the Nazgûl leads Sauron's forces against the successor kingdoms of Arnor: Rhudaur, Cardolan, and Arthedain. He destroys all of these, but is eventually defeated by the Elf-lord Glorfindel, who puts him to flight, and makes the prophecy that "not by the hand of Man will he fall". He escapes, and returns to Mordor. There, he gathers the other Nazgûl to prepare for Sauron's return.

Towards the end of the Third Age, Sauron sends the Witch-king, leading the other Nazgûl, to the Shire to find and recover the One Ring. He is cloaked and hooded in black; his face cannot be seen; he rides a black horse. At Weathertop, the Witch-king stabs Frodo, the bearer of the One Ring, in the shoulder with the Morgul-knife, breaking off a piece of it in the Hobbit's flesh. Frodo is able to see that the Witch-king is taller than the other Nazgûl, with "long and gleaming" hair and a crown on his helmet. He is swept away by the waters of the river Bruinen and his horse is drowned. He returns to Mordor. He reappears mounted on a hideous flying beast.

During the Battle of the Pelennor Fields, the Witch-king uses magic, including Grond, a battering-ram engraved with evil spells, to break the gates of Minas Tirith. He is faced by a single warrior, Dernhelm, actually a disguised Éowyn, a noblewoman of Rohan; and not far away, Merry, a hobbit of the Fellowship. Éowyn boldly calls the Nazgûl a "dwimmerlaik", telling him to go if he was not deathless. He casts back his hood to reveal a crown, but the head that wears it is invisible. Merry's surreptitious stroke with an enchanted Barrow-blade brings the Nazgûl to his knees, allowing Éowyn, the niece of Théoden, to drive her sword between his crown and mantle. Thus the Witch-king is destroyed by a woman and a Hobbit, fulfilling Glorfindel's prophecy. Both weapons that pierced him disintegrate, and both assailants are stricken by the Black Breath, which causes a cold paralysis, terror, and often death.

Megan N. Fontenot, on Tor.com, writes that in early drafts, Tolkien names him "the Wizard King", so powerful in wizardry that his opponent Gandalf is unable to counter him unaided. In early drafts of "The Council of Elrond", Gandalf explains that his enemy was "of old the greatest of all the wizards of Men". In a later draft, Tolkien adds that the Wizard King was also "a great king of old" and the "fell captain of the Nine [Riders]"; Fontenot glosses "fell" as implying "ravenous cruelty" and "ruthless ... savagery".

Later, in a draft of "The Siege of Gondor", Tolkien makes the Wizard King "a renegade of [Gandalf's] own order" from Númenor. In the manuscript of his notes for translators, Tolkien suggested that the Witch-king of Angmar was most likely of Númenórean origin. Fontenot comments that this could make him both a Maia rather than a Man, and originally one of the Istari, or, as she states, "something decidedly other". But Tolkien then reduces the Wizard King's power, so that Gandalf is able to tell Pippin as they wait for the attack on Gondor that "In him I am not overmatched", and that the Wizard King's main power is to inspire fear at a distance (with the Black Breath). At some stage, too, he renames the enemy the Witch-king; Fontenot suggests this was to distinguish more clearly between him and the Wizards like Gandalf and Saruman. Tolkien had thus explored making him a wizard (Istari or otherwise) or an immortal Maia, before settling on a "a human king whose lust for power got the better of his good judgment." She wonders what he might have been like before he accepted a Ring of Power from Sauron, noting that he was seemingly filled with "possessiveness, greed, lust, and a desire for dominance", all markers of evil in Tolkien's scheme of things.

The Tolkien scholar Tom Shippey writes that the Lord of the Nazgûl hovers close to being an abstraction, "a vast menace of despair ... a huge shadow", actually calling himself Death: "Old fool! This is my hour. Do you not know Death when you see it?" The scene forms, too, a picture of the "unexistence of evil", based on the Boethian philosophy that God is all-powerful, so evil is not the equal and opposite of good, but simply its absence: he forms "a huge shadow".

The theologian George Hunsinger compares Tolkien's depiction of the Witch-king to the theologian Karl Barth's analysis of evil. Barth's conception is embodied in his term das Nichtige, "nothingness", which Hunsinger glosses as "something dynamic and sinister ... an active cosmic power, a power of destruction, a power of chaos, negation, and ruin." The power of das Nichtige is both "outwardly repulsive" and in Barth's words "intrinsically evil"; it can be described but not explained, and is defeated by God; it is wholly evil and serves no good purpose. It is both fearful and empty.

Hunsinger states that Tolkien's account of the Witch-king as he confronts Gandalf at the gate of Minas Tirith "captures something of Barth's notion of das Nichtige." He finds it especially relevant that the Witch-king is "above all ... actual and yet empty at the same time", and comments that Tolkiens "dead but undead Black Rider is as good a symbol as any ... for Barth's impossible possibility."

Similarly, Hunsinger finds Tolkien's description of how Éowyn kills the Witch-king "an image for the paradox of evil as something powerful and yet hollow at the same time." He notes that her sword shatters with her final stroke, but of her defeated foe, "nothing is left" in the empty mantle and hauberk.

The Episcopal priest and theologian Fleming Rutledge writes that whereas the "pale king", the invisible Witch-king of Angmar, is striving to kill Frodo, the real king, Aragorn, who has been out of sight, in disguise as a Ranger, is doing all he can to heal him: the two kings are opposites. She writes also that while the enemy visible to Gondor is the Men of Harad and the Easterlings, the real enemy is personified by the Witch-king.

Fleming Rutledge's comparison of the Witch-king and Aragorn

Character	Kingship	Goal	Visibility
Witch-king	Was King of Angmar	To kill the ring-bearer Frodo	Actually invisible
Aragorn	Has claim to be King of Gondor	To heal Frodo	Has been out of sight as a Ranger

Julaire Andelin, in The J. R. R. Tolkien Encyclopedia, writes that prophecy in Middle-earth depended on characters' understanding of the Music of the Ainur, the divine plan for Arda, and was often ambiguous. Thus, Glorfindel's prophecy "not by the hand of Man will [the Lord of the Nazgûl] fall" did not lead the Lord of the Nazgûl to suppose that he would die at the hands of a woman and a hobbit.

Shippey states that the prophecy, and the Witch-king's surprise at finding Dernhelm to be a woman, parallel the witches' statement to Macbeth in Shakespeare's play of that name that he may "laugh to scorn / The power of man, for none of woman born / Shall harm Macbeth" (Act 4, scene 1), and Macbeth's shock at learning that Macduff "was from his mother's womb / Untimely ripp'd" (Act 5, scene 8), as Macduff was born by Caesarean section. Thus, Shippey notes, despite Tolkien's stated dislike of Shakespeare's treatment of myth, he read Macbeth closely.

The Tolkien scholar Michael Drout identifies a further parallel with Shakespeare, one of several allusions to King Lear in The Lord of the Rings. The Witch-king says "Come not between the Nazgûl and his prey", as the mad Lear says "Come not between the dragon and his wrath".

In Peter Jackson's 2001–2003 The Lord of the Rings film trilogy, during the siege of Minas Tirith, the Witch-king wears a distinctive helmet over his hood resembling a mask and a crown, rather than the crown worn underneath his hood in the book. The Witch-king's mount is largely responsible for the death of Théoden and his horse Snowmane, a departure from the book. As confirmed in the films' audio commentary, the design of the monsters was based largely on illustrations by John Howe.

In the first film of Jackson's 2012–2014 The Hobbit film trilogy, the Wizard Radagast briefly encounters the Witch-king while investigating the forest fortress of Dol Guldur.

Péter Kristóf Makai, in A Companion to J. R. R. Tolkien, writes that the 1976 board game Middle Earth provided the Witch-king with a choice of nine spells, against Gandalf's eleven. Some of these were shared, such as the ability to project a defensive lightning-bolt.

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