Onyx Storm is set to release on January 21, and the next Fourth Wing sequel must end one Empyrean Series trend after both Fourth Wing and Iron Flame did it. After Iron Flame's shocking ending, it's likely that the upcoming sequel will feature higher stakes and more tragedies as the war between Navarre and the venin continues. Even Onyx Storm's cover suggests a tonal shift, hinting that the book will be much darker than its predecessors. And with Onyx Storm shaping up to be different from Fourth Wing and Iron Flame, it must end an Empyrean Series trend.

Both Fourth Wing and Iron Flame see the return of a seemingly dead character, upending reader expectations by revealing new fates for these players. The end of Fourth Wing sees Violet learning that her brother, Brennan, actually survived the Tyrrish Rebellion. And Iron Flame undoes Fourth Wing's most satisfying moment by bringing Jack Barlowe back into the fold.