The dissolving Morgul blade

[Inziladun]

I'd like to add that perhaps any blade used by the Nazgûl to actually physically wound someone in the "light" world might be expected to vanish.
Since we see that a blade piercing a Ringwraith breaks and is destroyed, maybe contact with the truly living has a similar effect on "dark" weapons. Why this might be is uncertain, but maybe it's related to the nature of the Nazgûl, described as they are as hating light and living things, yet being attracted to them. The Nazgûl existed as extensions of Sauron's fea, and he, being a negative spirit of the dark, might impart some sort of anti-life/anti light into those who share his will and soul, which might filter down into specially made weapons intended for their use.

[Zigûr]

Originally Posted by Inziladun

The Nazgûl existed as extensions of Sauron's fea, and he, being a negative spirit of the dark, might impart some sort of anti-life/anti light into those who share his will and soul, which might filter down into specially made weapons intended for their use.

I think this is an interesting way of looking at it. Perhaps the blades were imbued with that same "nothingness" of which the Ringwraiths themselves were apparently composed.

It's worth comparing to the effect on Merry's sword as well after he stabs the Lord of the Nazgûl with it: it disintegrated too.

Both seem to hark back to Beowulf in which the giant-sword Beowulf uses to slay Grendel's mother dissolves in her blood, the suggestion being, I think, that evil things have a kind of matter-antimatter relationship with the world.

I never thought of it before but it would explain things if the Morgul-weapon dissolved in light, which would also explain why Merry's sword disintegrated almost immediately after he had used it - the shadow from Mordor notwithstanding, it was the middle of the day.

[Pitchwife]

I didn't mean a built-in timer, Leaf, and certainly not coincidence. The fact that the blade would dissolve eventually was built in, I think, but being exposed to the light certainly sped the process up - like iron rusts faster in water than in air.

Zil, I think you're on to something bringing the dualism of wraithworld and "light" world into the picture. Maybe the way the knife was to 'wraithify' its victim was by fading back into the wraithworld after it had pierced them and taking the victim with it?