I enjoyed this one a lot. I, too, was a bit upset by Mercedes' treatment of Vren at the end, until I considered all the lives he had previously helped destroy. Hundreds? Thousands? Sympathetic or not, he's a mass murderer (changing a person completely is basically the same as killing the previous person, IMHO). So I think he got what he deserves. He'll have the chance to do some good for the world for his freedom, to balance out all the bad he did for the exact same reason.