The thing that happen between chapter 21 and chapter 22 is the tone permanently changes to a more cynical attitude and this is the significant structural shift. The answer to this question is which asking about what happen between chapters 21 and 22 is that the tone permanently changes to a more cynical attitude.
I think its real....................................................wow
I am not 100% on this but crest is usually associated with a wave so if there is an answer for a wave I would go with that