The Iron Flame explained a shocking twist regarding Xaden that has huge implications for the upcoming third book, Onyx Storm. The first book in the Empyrean Series, Fourth Wing, saw Violet Sorrengail be thrown into the Riders Quadrant of Basgiath War College, forced to undergo the grueling and deadly challenge of becoming a dragon rider rather than the safer and more mundane role of a scribe as she'd trained. She meets and falls in love with the man she thought was her enemy, Xaden Riorson.

The second book, Iron Flame, finds Violet, Xaden, their dragons and their friends up against the threat of the venin. No longer mythical creatures in children's books or theoretical adversaries, venin are very real and have opened the first front in their war against the people of Navarre and Poromiel, defended only by the dragon riders of the former and the gryphon riders of the latter.