Thais follows Xül into the gardens and asks him why he doesn’t want to wed Nyvora. He says that she and all the other potential divine matches see him only as a “useful tool in their endless games” (299). He shows Thais a scar on his neck that he received when Nyvora and a group of other young Legends attacked him when he was 10. Ever since, he’s devoted his life to gathering secrets and building walls to keep himself safe.

Thais says that she and Xül are alike because both of their lives seem governed by fate. He admits that he’s drawn to her because she doesn’t try to flatter him: “Everyone sees what I represent, what I can provide. But you…you just see me. The good and the terrible alike” (304).

He embraces her, but the moment is interrupted by an announcement that Thalor, Aesymar of Water, and Sylphia, Aesymar of Wind, will oversee the second Trial at dawn the next day. Xül and Thais hurry back to the Bone Spire. With so little time to prepare, he encourages her to rest rather than strategize and offers for her to sleep in his chambers. She reluctantly declines.

The next morning, the contestants gather in the world of Hydrathis. Thalor and Sylphia give them the ability to breathe underwater and instruct them to “find three keys to unlock the Siren’s Archive” in the drowned city of Memorica (311), which lies at the bottom of a lake. Thais and Thatcher find two keys that show them the final moments of people who drowned in Memorica. Their ensuing horror manifests in the form of aquatic monsters, but they banish the creatures by quelling their fear. Suddenly, Thais is pulled into a vortex.

Inside the cyclone, Thais has a vision of Thalor drowning everyone in Memorica. Her fear manifests as a shark the size of a ship, and both her fear and her self-preservation instincts temporarily vanish when she slays the monster. She reunites with Thatcher, Marx, and Kyren, and the group gathers the remaining keys. Together, they uncover the events behind the city’s demise: Memorica’s priests sold divine knowledge that mortals aren’t meant to possess, and Thalor destroyed the city to avenge their betrayal of his trust. The group enters the Archive and encounters sirens who instruct them to reveal their deepest secrets.

Marx reveals that she cursed her family when she ran away, causing them to die horrible, painful deaths. Kyren reveals that he destroyed his parents’ lives by using his illusions to fraudulently increase their business profits. When only the twins remain in the Archive, Thais tries to trick the sirens by claiming that her darkest secret is the satisfaction she felt when she took her fellow contestant’s life. However, they see through her deception and torture her. To save his sister, Thatcher unleashes his Primordial power and destroys the sirens. As the Archive begins to collapse around them, the twins swim for the surface.

Only 18 contestants pass the Trial. Some are unable to complete it because the twins destroyed the Archive. Thalor and Sylphia want to disqualify the twins, but Xül defends their actions. Olinthar appears and states that Thais and Thatcher can’t be disqualified for breaking the rules because Thalor and Sylphia never told them that they had to speak their darkest secrets to pass. In fact, he commends them: “Creativity in the face of impossible choices is precisely what we should value in potential ascendants” (352). Using their telepathic link, Thais tells Thatcher about Olinthar’s plot to merge his world with the Domain of War. She resolves to “see Olinthar dead if it was the last thing [she] ever did” (354).

The narrative moves to Thatcher. Olinthar asks to speak with him privately in Sundralis, which seems cold and sterile despite the eternal daylight that fills the world. Olinthar calls Thatcher’s unprecedented Primordial power “a blessing of the greatest magnitude” (357), asks him to consider living in Sundralis after he ascends, and advises him to be careful whom he associates with.

The narrative returns to Thais. Xül brings her to the ruins where Vivros battled Moros, the Primordial of corruption. Vivros emerged victorious, but he was corrupted. This led to the first divisions among the Aesymar as they split between “[t]hose who would destroy what they fear versus those who would understand it” (363). The former prevailed and destroyed Vivros.

Xül warns Thais that the gods see Thatcher as a terrible threat or a potential weapon because he possesses Vivros’s power. She considers returning the trust he has shown by revealing her and Thatcher’s plot against Olinthar but decides against it.

During a training session, Xül observes that Thais has only unleashed her full power during moments when she’s overwhelmed with desperation or desire. He tells her to “work with [her] true potential, not against it” (373). With her permission, he pins her against a rock and kisses her. When he lets go, she succeeds in forming a crown of pure celestial energy.

When Thais returns to her chambers, she has a sexual fantasy about Xül but then tells herself to focus on her revenge scheme, not a “flirtation that walked the edge of destruction” (374).

Xül spends five days away from the Bone Spire, delegating Thais’s training to Aelix. During a private conversation, Thais assures Marx that she doesn’t judge her for killing her family, and Marx deduces that the twins have a divine parent.

Kavik attacks Thais with an army of fire beasts, robotically repeating the words, “The girl is a threat. She must be eliminated” (385). Thais has to unleash more power than her mortal body can safely hold to keep the beasts at bay. Xül appears, summons corpses that drag Kavik into the earth, and begs Thais not to leave him as she falls unconscious.

Three days after the attack, Thais awakens in Xül’s bed. She had a night terror about Sulien’s death and tells Xül what happened to him, and he shocks her by saying that the gods have lost their sense of justice. They don’t know who sent Kavik or why, so they decide to keep the attack a secret for the time being.

Xül reveals that he was away from the Bone Spire because his father was arranging an engagement between him and Nyvora. Thais urges him not to go through with the wedding, but he says that he must fulfill his duties to his realm.

Xül tells Thais about the events that led to the battle between Vivros and Moros. Originally, there were 13 Primordials, but Moros weakened the others by feeding on their memories. The original 12 Aesymar took advantage of this and slew 10 of the Primordials.

Xül explains that the Aesymar were originally one of four distinct pantheons, each with its own mortal realm to rule. The deaths of the Primordials scattered the four realms in what is called the Sundering. Thais realizes that the Aesymar hide this truth to keep mortals from questioning their power and that they use the Trials as a way of eradicating or assimilating anyone who could potentially usurp them. Xül advises her to conceal her knowledge of the Sundering and its implications because she already has “a rather large target on [her] back” (409).

Syrena, Aesymar of Illusions and Desires, invites the surviving contestants and their mentors to a ball. While Xül teaches Thais a dance for the event, they share pieces of their early lives with one another, such as the time he secretly saved a mortal child’s life and the time she nearly ran away from home when she was 16.

When Xül asks what she plans to do after the Trials, she admits that she doesn’t think she’ll survive. Xül refuses to accept this answer: “The Thais I know […] wouldn’t accept death as a foregone conclusion—she’d rage against it” (420). She counters by pointing out that he’s resigned himself to “a hollow, empty life” (420). Still, he urges her not to abandon hope, and she begins to imagine a future in which she fights for her own survival as well as vengeance.

Thais and the other disoriented contestants awaken in Asteria, the Domain of Dreams, where they receive spa treatments and are prepared for the ball. Lyralie and her fellow Dreamweavers dress Thais in a crystal-covered gown that looks as though it’s made from “liquid starlight.” An attendant brings Thais a luminous beverage, but Lyralie makes sure that she doesn’t finish it, warning her that “[n]othing is what it seems” (430).