The third part of the fantastic series set in a world where magicians travel between parallel versions of London. It continues the story of "A Darker Shade of Magic" and "A Gathering of Shadows." The author also wrote "Vicious" and "This Savage Song."

Summary of the story: The fall of London and the rise of the kingdoms as darkness engulfs the Maresh Empire, and the fragile balance of magic shifts into dangerous territory while the heroes fight.