Hmm. What do readers expect from the book?
An unexpected twist, a good book should break their ideas. The reader should be forced to doubt what is happening and the possible outcomes that he has created for himself.
But how to do it?
Kill all the heroes? a traitor? Is this all a dream? A dead hero who turned out to be actually alive?
All this is banal. The reader should be shocked, surprised, maybe even scared. And all these examples have already been in other books.
Then what unexpected twist should there be?Which unexpected twist will work?