[Legate of Amon Lanc]

Originally Posted by Lalwendë

Yet it was the 'Morgul-blade' that was almost the cause of Frodo becoming a wraith, not the Ring, though that helped the Ringwraiths to hurt him. Again, an artefact with magic of some kind wrought into it? Or just a blade which inflicted a terrible injury, but with the consequence that as a Ringbearer he would become a wraith rather than die?

Originally Posted by jallanite

There is no indication that a wound from a ‘Morgul-knife’ with pieces of the blade within would have gradually changed only a Ring bearer into a wraith. It seems to me likely enough that if the leader of the Ringwraiths had stabbed Sam, or Merry, or Pippin, or Aragorn, the same thing would have happened to that person.

The part word morgul- means ‘black magic’ (mor ‘black’ + gûl ‘evil sorcery’).

Possibly because Frodo was a Ring-bearer he had increased susceptibility to a morgûl wound. Or possibly the Ring actually helped Frodo to resist the enchantment. We are not told either way. Aragorn’s athelas helped, but some fragments of the blade had gotten in too deep for Aragorn to find them.

But a knife that was otherwise normal but inflicted a horrible wound would probably not be called ‘Morgul-’ by Gandalf, its blade would not have vanished away in the light, and Aragorn and Glorfindel both would not have been so concerned. Glorfrindel in particular refers to signs written on the surviving hilt which he doubts the others can see but which are evil.

The "Morgul-blade", I have always believed is simply called after Minas Morgul, the "capital city of the Ringwraith", so it would be the place of its making (or the place where it "comes from" in the eyes of the outside world). But of course that does not dismiss the fact that Morgul does mean "black sorcery", and of course that is where the name of Minas Morgul (or Imlad Morgul) comes from.

But yes, the essential part is correct: the blade would have made anyone a Wraith in time. We are told about the shard that remained inside Frodo for a long time, and was traveling towards his heart. But I think the Ring sped up the process. Simply put: if somebody keeps wearing the Ring for long, he starts fading. If someone is stabbed by a Morgul-Blade, he starts fading. This is just adding the two of them together.

For reference, emphasis mine:

Originally Posted by LotR, Book II, Chapter I: Many Meetings

"Elrond is a master of healing, but the weapons of our Enemy are deadly. To tell you the truth, I had very little hope; for I suspected that there was some fragment of the blade still in the closed wound. But it could not be found until last night. Then Elrond removed a splinter. It was deeply buried, and it was working inwards."
Frodo shuddered, remembering the cruel knife with notched blade that had vanished in Strider's hands. "Don't be alarmed!" said Gandalf. "It is gone now. It has been melted. And it seems that Hobbits fade very reluctantly. I have known strong warriors of the Big People who would quickly have been overcome by that splinter, which you bore for seventeen days."
"What would they have done to me?" asked Frodo. "What were the Riders trying to do?"
"They tried to pierce your heart with a Morgul-knife which remains in the wound. If they had succeeded, you would have become like they are, only weaker and under their command."