system
A chat on subreddit /r/PoliticalCompassMemes
human
The prophecy was "Do not pursue him! He will not return to these lands. Far off yet is his doom, and *not by the hand of man shall he fall.*" Characters with a sense of magic don't speak lightly of the future, and due to the nature of Arda and how everything works, it can have lasting implications when they do. Magic in the Tolkien world relies very heavily on the spoken word, you won't see much magic done on either side without an incantation of some kind.

&gt; Éowyn: Do what you will, but I will hinder it, if I may.
&gt;
&gt; Nazgûl: Hinder me? Thou fool. *No living man may hinder me!*

This was just the witch king gloating about how powerful he was, *completely unaware of the prophecy,* and was before he was stabbed in the knee by Merry. He would have been nearly invincible to Eowyn's attack regardless of her lack of nads. The dagger used was of the same ancient magic as him, and temporarily unbound his physical body from protective magic. He unknowingly referenced the prophecy, broke her shield and arm with one swing of his mace, got stabbed with a magic dagger, and Eowyn stabbed him in the face with a regular sword while the magic was gone. Any man *could* have swooped in and done it, but that's not how you write a good story.
gpt
"No *living* man" is also important. He fell by a woman's hand after being "hindered" by a hobbit with a dagger that a long-dead man had made for that purpose.

The Witch King left far too many loopholes in his magical immortality clause.