He drinks the wine in the last panel because the second to last panel is the beginning of what he said in panel #14.
And because Tarquin's world really is a world that follows narrative tropes, Elan really is trapped in this story precisely because that is a good story.
The only way Elan can escape from it is figure out how to transform it into some other sort of story. And since that isn't going to be easy, this story line is likely to persist for a while.