One of the book’s main themes is the concept of power, which begs the question, what is true power? The most obvious answers are the gods’ power, political/social power, and magical power, but identifying “true power” from these options is not so simple. The gods’ power can be overcome by magic, as seen through Aeëtes’s ability to heal Circe from Helios’s wrath. It can also be circumvented by political power, as proven by Circe’s extortion of her father’s assistance as well as Athena’s unwillingness to risk war with the Titans by killing Circe. However, political power does not always triumph over witchcraft, as shown by Helios’s fear of Aeëtes’s magic and Pasiphaë’s control over her husband. Still, magical power does not stop Circe’s exile or Medea’s divorce.

Throughout the book, these different types of power are often in contrast. When a character finally achieves one kind of power, they discover that they are still at the mercy of another. Inherently lacking political power as a woman and a nymph, Pasiphaë uses her magical power to threaten her husband so she can live in relative safety. Similarly, Medea lacks the political power to create a life of her choosing.