Fire
Fire is a common symbol in literature. In Empire of Storms, it is symbolic of Aelin's magic. She uses fire initially to destroy things, but also to purify them and turn them into something new and better.
Queen Maeve's crown
Queen Maeve's crown, which she steals from Aelin, is symbolic of power and the weight of the kingdom. The person who controls the crown inevitably ends up controlling the kingdom, the kingdom's subjects, and much of the land generally.
The Bane
The Bane, Aedion's army, is a powerful symbol of the potential for change under the threat of violence. When people or institutions are threatened with violence in a very way, they are more apt to enact changes. Armies can be influencing forces and can enact the changes they want through sheer force of will.
Finding help
To defeat Queen Maeve and other sinister forces, Aelin and her friends are fairly consistently forced to seek out the help of unforeseen allies. This motif underscores the grave nature of the threat that Aelin and her friends are facing.
