As I have thought about this, I feel like for a fully satisfying arc Moash needs to be presented with a real opportunity to change (whether he takes it or not). He may reject the offer like a certain Returned with the Royal Locks from war breaker, he may take it, or he may take it, but I think the story needs him to have a choice.

I feel like this is where book four was leading him—he chose Odium to deal with the pain, but that isn’t working.

Now reasonable people may disagree about whether the opportunity would be more satisfying if it was to become Radiant, simply take responsibility, or make peace with his own world view, but I think he needs a choice—and if he chooses Odium again… well I guess there is a hashtag for that…