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 a battering-ram engraved with magical spells.
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.
[T 3] 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.
[T 5] 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.
[T 14][T 15] During the Battle of the Pelennor Fields, the Witch-king commands Grond, a battering-ram engraved with evil spells, to successfully break the gates of Minas Tirith.
Being forced to leave the broken gates he retreats to lead the besieging army against the new threat of the Rohirrim, where 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.
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.
[T 14] 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.
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.
"[2] 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",[T 19] actually calling himself Death: "Old fool!
[6] 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.
"[6] 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.
"[6] 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."
[7] 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.
[8] The Tolkien scholar Michael Drout identifies a further parallel with Shakespeare, one of several allusions to King Lear in The Lord of the Rings.
[14] 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.