“Do you humans no longer understand mercy?” he said, his fangs inches from my throat. “Let me make this clear for you, girl: you can either come live at my home in Prythian—offer your life for the wolf’s in that way—or you can walk outside right now and be shredded to ribbons. Your choice.”

Tamlin first presents the terms of the treaty to Feyre in Chapter 4 as an act of mercy, but neither of them fully understands how powerful that mercy will turn out to be. The treaty is a farce, but Tamlin’s grief and rage over Andras’s death are real. In reality, Tamlin is aware he must bring Feyre back to Prythian to break the curse, but his choice to treat her well is his own. Tamlin takes her to his manor house and shows her kindness, courtesy, and comfort, which allows her to grow and heal from years of poverty and stress. As a byproduct of his mercy, the love necessary to break the curse begins to form between them. Though he takes Feyre to Prythian under false pretenses, his mercy is real. Ironically, while Tamlin begins with a selfish motive, the mercy he shows Feyre does allow her to heal.

"I regret what I did to Andras,” I said, the words so strangled they were no more than a whisper. “I regret that there was…such hate in my heart. I wish I could undo it—and…I’m sorry. So very sorry.”’

In Chapter 17, Feyre’s interaction with a dying blue faerie is the catalyst for her realization that her hatred towards faeries is unwarranted. As the blue faerie suffers and dies before her eyes, Feyre realizes that faeries are just as deserving of compassion as humans. In a moving scene, Feyre holds the hand of the blue faerie and offers him soothing words because she doesn’t want him to die alone and afraid. Her act of mercy shows that she’s beginning to understand that humans and faeries are not so different. This moment allows her to feel genuine regret for killing Andras in wolf form, and she expresses this to Tamlin for the first time. For Feyre’s entire life, she believed killing faeries was justified for all their kind had done to humans, but she now understands this to be ignorance. Her mercy does not heal the blue faerie, but it heals Feyre’s hardened heart.

"For what she gave,” Rhysand said, extending a hand, “we’ll bestow what our predecessors have granted few before.” He paused. “This makes us even,” he added, and I felt the twinkle of his humor as he opened his hand and let the seed of his light fall on me.”

As Feyre lies somewhere between life and death in Chapter 45, the High Fae come together to heal her with their mercy. Feyre has overcome her prejudices against faeries and sacrificed her life to save them from Amarantha’s rule. In return, the High Lords decide to show her mercy. Recognizing that Feyre will die without their intervention, each of the High Lords bestows Feyre with a piece of their light. This act of mercy is significant because the gift of light from the High Lords is rare and not only brings her back to life but transforms her into a powerful faerie herself. At the novel’s climax, the mercy granted by each of the High Fae in exchange for Feyre’s bravery offers the ultimate healing, turning her into an immortal High Fae.