[dancing spawn of ungoliant]

Originally Posted by SpM

The whole point is that Aragorn as the true heir of Isildur, the one who cursed them, and wielding Isildur's sword, is the only one capable of challenging the King and holding him and his people to their oath.

I think Sauce strikes the nail on the head.

Originally Posted by The very same Guy with Pans

Perhaps they have a choice in whether they kill those who they swarm over

Maybe. But that, I think, leads us to a question about what made the Dead so... deadly.

Originally Posted by RotK, The Last Debate

And suddenly the Shadow Host that had hung back at the last came up like a grey tide, sweeping all away before it. ... Pale swords were drawn; but I know not wether their blades would still bite, for the Dead needed no longer any weapon but fear. None would withstand them. ... And all marines were filled with a madness of terror and leaped overboard.

In the movie we see that grey (or green) tide and they just float over the enemy swinging their swords. In the book it seems that they used mostly fear instead of physical whacking abilities. Later it is told that at the end all enemies drowned or fled so the ghosts didn't/ couldn't kill all of them. So, did the orcs and other nasty things just get a heart-attack and die? Maybe not.

Originally Posted by Eomer

Yet his sword makes real contact with Aragorn's sword.

I'd be interested to know, what would have happened if Aragorn hadn't been able to stop the Dead King's strike. Would he have been able to wound Aragorn?