One more question?
What is the "Black Breath"?
er...that would be g'nad after a few too many Irish Car Bombs...
Bubonic plague.
Oh, you said "breath", not "death". Some sort of biochemical warfare is my best guess.
It's never really explained explicitly, but it is one of the evil effects of the Nazgul, like a spell of some kind. If I remember correctly, there are only a couple instances of it in the book - Merry in Bree, and Faramir. Maybe Eowyn too. Merry describes it as "I thought I had fallen into deep water... I had an ugly dream, which I can't remember. I went to pieces. I don't know what came over me."