User blog comment:Thornclaw Braveheart/Witch-king of Angmar vs. Eragon Bromsson/@comment-4555900-20111201014216/@comment-2006360-20111202111150

I made some explanations above. Jierda is a spell that causes things to break. Black Breath is an acidid smoke released from a Nazgul that acts much like a nonlethal gas attack. Black Shadow is related to Black Breath, and infect people.