Nevelen feather. Nevelen's wings are brutally chopped off when they are inducted into slavery, leaving them with deep, bloody scars on their backs. Nicolette realizes that she had a dress sewn out of Nevelen feathers when she was a girl, and it causes her to be sick.
Hush Hush series--reading these right now. If you were a fan of Twilight then this is a good one to read. Not vampires but another form of Paranormal romance. Very addicting reads. Read the first one in Less than 24 hours.