The theme of vengeance guides the dark romantasy novel’s tone and structure just as the characters’ missions of vengeance transform themselves and their realm. Although Morthus shares Thais and Thatcher’s goal of ending Olinthar’s corrupt reign, the characters are willing to pay very different prices for their revenge.

Thais and Thatcher’s plot to destroy Olinthar shapes the novel’s plot and deeply changes both siblings. For years, Thais secretly dreams of making the King of Gods “pay for what [he’d] done to [their] mother, to countless others” (21). When Olinthar’s laws regarding Blessed Mortals bring about Sulien’s death and force the twins into the Trials, he inadvertently gives them the opportunity as well as further motive to realize this goal. Although Thais eventually kills Olinthar, her revenge comes at a heavy price. On top of causing her physical pain and psychological trauma, the Trials and Forging erode her sense of identity. She compromises her long-held values by taking her fellow contestants’ lives, and ascending to godhood makes her more like the divine father she despises. The authors underscore the cost of revenge by making Thais inherit Olinthar’s powers when she kills him: “I’d hated the spark of him in my blood. Now I carried the whole fire. The universe, it seemed, loved its cruel symmetries” (710). This inheritance literalizes the idea that Thais’s quest for vengeance risks turning her into the very thing she loathes.

The twins’ revenge mission similarly changes Thatcher. He becomes close to Olinthar so that he can spy on him, and this requires him to commit deeds that he abhors, such as killing a spy. Of all the characters, Thatcher pays the steepest price to claim vengeance. At the end of the novel, he loses everything in the battle with Olinthar and Moros, is cast out of his universe, and is robbed of all his memories of his beloved sister and his own identity. His transformation, like his sister’s, reveals that the pursuit of vengeance irrevocably changes the avenger.

In contrast to the twins’ self-sacrifice, Morthus makes others pay the price of his revenge. The God of Death is a complex figure because his cold and calculating deeds are driven by righteous anger at Olinthar’s corruption and compassion for the suffering of mortals. He has built his life around meticulously planning a coup that will reshape the distribution of power in the cosmos: “‘The mortal realm has beauty,’ Morthus said, his tone softening. ‘But also unnecessary strife. Poverty. Disease. Suffering that continues not because solutions don’t exist, but because we choose to withhold them’” (584). However, to improve countless lives, Morthus is willing to commit brutal deeds and manipulate even his loved ones. This is most clearly seen when he forces his son into an arranged marriage in exchange for Thais’s life: “I will not abandon my goal for this, Xül. Not for her, not for you, not for anything. We’ve worked too long, sacrificed too much to let chaos destroy everything now. The pantheon must change. The old ways, the cruelty, the endless power games—they die with Olinthar” (705).

The irony of Morthus seeking to put an end to “power games” by manipulating his son into an unwanted union speaks to a key element of the resolution’s tragedy: the way that Morthus’s belief that the ends justify the means makes the characters question whether all their struggles have amounted to “merely replacing one tyrant with another” (583). Grenwich and Lennox’s examination of revenge raises the novel’s suspense as well as ethical questions about the cost of vengeance and the nature of justice.