When magic has gone from the world and a vicious king rules from his throne of glass, an assassin is summoned to the castle. She is a prisoner, but if she can defeat twenty-three killers, thieves, and warriors in a competition, she will become the King's Champion and earn her freedom. But the evil she encounters in the castle goes deep, and as dark forces gather on the horizon-forces that threaten to destroy her entire world-the assassin must take her place in a fight greater than she could ever have imagined.