Their name is Angel. They found out who was responsible for the Song River incident.

So in return, they cut out every vocal cord of any Acidia they could find.

For all the melodies that can never be sung again, I'll make sure that others lose the same.

[You'll find your neck suddenly sliced open, blood spilling out and vocal cords cut. You find you cannot talk, although you don't die. If too much blood gets spilled, it slowly seeps back into your body, but it will eventually flow out again.]