My booklet says Arhys, but when I heard it, I just took it as a clear misprint. Has to be Daryus.
He has no more speaking lines, but after mistakingly attacking Faythe, i'd hazard a guess that he did the bolt. The last we hear in the title track, Arabelle says:
My Prince, My Son,
You got lost along the way,
In light of this new burden that you face,
You are forgiven on this day.
So, disappointed in him no doubt, but ultimately forgiven.
Even though Nafaryus is depicted as a pretty cold-blooded ruler, I kind of like how the Empire have that real sense of family. It's a neat touch in the story.