The novel examines how theology can be morally inverted into evil when faith becomes uncritical and religious institutions grow corrupt. Author Jay Kristoff deliberately stages violence and corruption in “sacred” spaces such as cathedrals to demonstrate the ease with which evil can subvert all that is holy. Since violence wears the garb of piety in such spaces, it can go unchecked for a long time. Moreover, by refusing to question the tenets of faith, characters end up perpetuating the injustice they have inherited. The novel therefore suggests that examining beliefs and religions is critical to the mission of resisting oppression and building hope in a bleak world.

The reason Ilon, the Priori of Whispers, is able to sustain for decades in Leon is because he acts through the instruments of the dominant religion of his world, known as the One Faith. Ilon is able to hide in plain sight because he has bewitched the bishop and a devout population through corrupting their sacrament. Since the populace cannot imagine their bishop—a figure of uncritical reverence—being enthralled, they become easier to dupe. It takes the objective, critical eyes of outsiders like Gabriel and Aaron to sense that the corruption has taken hold in the most sacred of spaces. 

In a manner similar to Ilon, the Esani order too manipulates the symbolism and vocabulary of faith to achieve their evil ends. Wulfric refers to murder and the consumption of souls, a blasphemous act, as “communion” and believes his order will achieve salvation on Judgement Day. Margot thinks of engineering the end of the world as a divine duty. Because Wulfric and Margot weaponize religious language, they are able to disguise their selfishness—the desire to live forever—as a noble or exalted calling. Celene nearly gives in to this manipulation, till she uses her love for Dior to resist the brainwashing. 

The perils of uncritical faith and institutional corruption is reflected in the silversaint order. The order is “holy,” but Celene reflects that she did not seek help from it after she was turned by Lauren because the silversaints abhor vampires on principle, without trying to understand the making of a vampire. Lachlan embodies the rigidity of the silversaints when he denounces Aaron at the onset of the novel, quick to believe the worst of him. Gabriel is cast out of the silversaint order because he falls in love with Astrid and she becomes pregnant with their child. Thus, an order meant to punish evil ends up abandoning the values of humanity.  

Although power-hungry figures and institutions weaponize the iconography and language of religion to oppress others, this oppression can be encountered by asserting the “real” or core humanistic tenets of faith, such as love, sacrifice, and solidarity. When Voss corrupts holy symbols such as the Dior’s blood at the site of the death of the Redeemer, the characters band together to destroy him. The characters who destroy him, are far from devout followers of faith, and include outcastes like Gabriel, Aaron, Baptiste, and Celine. Even Dior is an ambiguous figure, since she possesses both Divine powers as well as pagan magic because of her duskdancer heritage. Thus, the novel asserts that true faith is that which people hold in each other.