Boggart

A boggart has no body of its own that the stories are willing to show. It waits in closed dark spaces and wears your fear. That makes it a perfect classroom creature: the lesson is public, the fear is private, and the charm Riddikulus asks for comedy on purpose.

Nobody’s boggart is a personality quiz with a correct answer. It is a snapshot of what you cannot stand to see. The books let those snapshots be funny and, a moment later, not.