This review will contain spoilers for the rest of the Throne of Glass series, up until Queen of Shadows. If you have not read up till Queen of Shadows, read at your own risk.
Aelin Galythinius needs to find an army if she wants to win this war. Empire of Storms begins with Aelin and the ‘gang’ (by which I mean Rowan, Lysandra and Aedion) entering Terrasen and finding out that things aren’t going to be quite as easy as Aelin walking up to a throne and pronouncing herself the Queen. Terrasen has been beaten down since the assassination of Aelin’s parents and has grown poorer and poorer since it’s been under Adarlan’s rule. To put it simply: they aren’t in the best place for a Queen who is going to war. With this in mind, and Dorian in potential danger, the ‘gang’ head south to see if they can find allies there.