Rebecca Yarros released "Onyx Storm" on January 21, but readers are already looking forward to the next book in the "Fourth Wing" universe.

Meet your potential Fourth Wing cast, from Josh Heuston as Xaden Riorson and Mackenzie Foy as Violet Sorrengail ...

After Onyx Storm's cliffhanger ending, readers have begun to put together many convincing theories as to what will happen next in the Empyrean Series.