A significant subplot involves Jules, who is pushed into the role of the "Legion Queen"—a figurehead for a rebel army intended to usurp Katharine. Her journey explores the theme of individuals being defined by the expectations of others versus their own desires. A Changing World

The book highlights that winning the crown is not a "happily ever after". Katharine’s isolation and growing paranoia underscore the high cost of sovereignty in a fractured realm. Identity and the Call of Duty

Katharine’s rule is haunted by whispers of her being "undead" or "cursed". She is literally possessed by the spirits of dead queens, which grants her power but also forces her into acts of violence against her will.

Two Dark Reigns expands the series' world-building by introducing mainland perspectives and delving into the mythology of the Blue Queen. Two Dark Reigns (Three Dark Crowns, #3) - Goodreads

While Katharine struggles in the capital, her sisters, Arsinoe and Mirabella, attempt to forge new identities on the mainland.