Thais Morvaren lives in a fishing village called Saltcrest with her twin brother, Thatcher, and their adoptive father, Sulien. The 26-year-old woman can create objects out of starlight. Her mother conceived her after Olinthar assaulted her, and delivering a half-divine child killed her.

Thais must keep her power a secret to avoid being forced to compete in the Trials of Ascension, which occur every decade and kill most participants. The Trials are scheduled to begin in two weeks, and the priests of the Aesymar sail to Saltcrest to search for Blessed Mortals. Sometimes, Thais fantasizes about using her powers to seek vengeance against the gods, but Sulien made her promise to conceal her abilities years ago.

Because of her divine parentage, Thais possesses superhuman strength and beauty. At Sulien’s request, she spends the day fishing out at sea so that she’ll be away from the priests who’ve come to the village. That evening, she and her father have an argument after he asks her not to drink while the priests are in Saltcrest because he fears that she will lose control of her growing powers.

Seeking an escape from her guilt and frustration, Thais visits her lover, Marel. When the couple has sex on a cliff, her power overflows and rearranges the stars into brightly glowing “spirals and flowing curves” (35). Terrified that the whole village will see the transformed sky, Thais dismisses Marel’s concerns about her and quickly takes her leave.

The narrative moves forward two weeks. The people of Saltcrest gather in a cave to celebrate a holiday called Last Light. Marel tells Thais he wants to marry her, and she feels guilty because she doesn’t love him.

One of the villagers tells a traditional story about Morthus, “Aesymar of death and King of Draknavor” (43), who fell in love with a priestess named Osythe and married her even though unions between immortals and mortals are considered “an abomination.” The priestess refused her husband’s offer of divinity, so he slowed down her aging process instead. Their son, Xül, ascended in the last Trials.

Thais is afraid that her powers will be discovered at the festival the next day, and Sulien tells her he loves her and is proud of her no matter what happens. Suddenly, a group of priests interrupts the celebration.

The priests’ leader declares that they “witnessed quite the display above [Saltcrest’s] cliffs” and know that there is a Blessed Mortal in the cave (50). The priests seize Marel because he was seen on the cliff where the stars rearranged themselves. Unable to stand by, Thais steps forward and declares, “I’m the one you want. Let him go” (52). To prove that she is the Blessed Mortal they’re looking for, she calls down starlight into her hands.

The priests bind Thais with magical ropes that block her abilities and seize Thatcher despite her protestations that he doesn’t have powers. The penalty for concealing Blessed Mortals is death, and Thais faints as the priests execute her father.

Thais awakens alone in a cell. Overwhelmed with grief and guilt, she thinks of her father’s death and his last words: “I love you both. Remember that. Always remember that” (58). She and her twin possess a telepathic link, but she’s unable to sense Thatcher. Thais demands to be taken to her brother.

A Dreamweaver named Lyralei, who serves the Aesymar of Dreams, offers to help her if Thais cooperates with the preparations for the Proving ceremony. Thais agrees, and her mental link to Thatcher is restored as soon as she’s released from her cell. Lyralei encourages Thais to ask to compete early so that she has a chance of securing the Legends’ favor and persuading them to spare her brother’s life. As Lyralei and her fellow Dreamweavers bathe Thais and dress her in a black gown covered in “thousands of tiny crystals” (64), she formulates a plan to save Thatcher.

Lyralei tells Thais that only 50 Blessed Morals survived out of the 200 who underwent the last Proving process. Of those 50, only 5 completed the Trials and ascended to godhood. She also explains that the divine realm of Voldaris, where the Trials will be conducted, consists of 12 separate worlds connected by portals. When Thais expresses surprise at the Dreamweaver’s kindness, Lyralei answers, “Not all who serve the divine realm agree with every tradition we’re asked to uphold” (71).

A portal takes Thais to an arena where seven Legends preside over the first group of Blessed Mortals. Thais feels intimidated by the deities, particularly Xül. When the Blessed are told to demonstrate their powers, Thais lowers all of the careful limitations she’s imposed on her abilities and bathes the arena in starlight.

A Legend named Drakor claps condescendingly after her demonstration and comments that “there’s still no blood on the floor” (78). The competitors fight to the death, and Thais defends herself with a sword she fashions out of starlight. As she braces herself to kill for the first time in her life, the Legends call off the match. She and a man named Vance are the only survivors. Thais asks the Legends to free her brother, pleading that “the Aesymar would not allow the murder of someone unable to defend themselves” (81). Some of the Legends are intrigued by the prospect of sibling drama.

The Legends teleport Thatcher to the arena. Thais hugs him and promises that everything will be all right. Drakor points out that Blessed Mortals’ powers can lie dormant, and he tortures Thatcher in an attempt to reveal any latent abilities. Xül objects to his fellow Legend’s methods, but he doesn’t stop Drakor. After “[m]inutes that felt like hours” (85), Thatcher’s eyes flash silver and take on an “ancient and terrible and utterly feral” expression (85). With a furious scream, he manifests his powers and makes Drakor implode.

The twins are placed in an opulent but locked suite. Thais tries to strategize about their next move, but Thatcher is in shock and fears that the Aesymar will kill both of them for what he did to Drakor. The siblings voice their grief over Sulien’s death. Thatcher believes they’re both to blame, but Thais argues that the blame lies with the gods and the “twisted system that treats mortals like they’re disposable” (91). Thatcher says that it might be better for them to die as mortals rather than join the gods they despise. Suddenly, Thais realizes that she could achieve justice for Sulien, her mother, and the countless other lives the gods have ruined by killing Olinthar. When her brother is unable to talk her out of this dangerous plan, he convinces her to let him help.

In the morning, guards escort the twins to separate dressing rooms. Lyralie and her team of Dreamweavers reveal that Voldaris is abuzz with gossip about the mortal twins who killed a god. The other gods viewed Drakor as a “monster,” and the Aesymar are intrigued rather than angered or frightened by his death.

Lyralei reveals that only 37 of the 300 competitors made it through the Proving. These survivors will be chosen by Legends who will become their mentors and prepare them for the Trials. This training not only involves honing their abilities but also learning to navigate divine society. Lyralie cautions Thais that the mentors expect “absolute obedience and complete dedication” from their mentees (100).

Thirty-seven Legends gather to select their mentees from the surviving contestants, and they are “utterly and completely intrigued” by Thatcher (102). When Chavore, the son of Olinthar, chooses Thatcher, Xül objects because the mortal’s power better aligns with his own Domain of Death rather than Chavore’s Domain of War. Reluctantly, Xül instead chooses Thais. She’s anxious that she and her twin are assigned to two gods who despise one another, but Thatcher tries to reassure her that their mission to take down Olinthar is progressing well: “Who knows a father better than his son?” (107).

As the Legends and their mentees disperse, Thais hurries to her brother. Fearing that this may be the last time they see each other, she hugs him and tells him, “I love you. And we’re going to make it through this” (109). Then she steps through a portal into Draknavor, the land of the dead.

Thais finds herself oddly drawn to the world, where an ocean stands beside a black castle called the Bone Spire. She asks Xül what she’s supposed to do now, and he dismissively tells her that his staff will tend to her; he then retires to his quarters. Furious, Thais storms out of the castle and swims naked in the sea. The water helps her regain her sense of self, and she practices using her power. She sees Xül watching her from his window, and she returns his gaze defiantly.

The narrative moves to Thatcher, who is in Bellarium, the Domain of War. A nightmare about killing Drakor wakes him, and he thinks of Sulien and his pledge to seek vengeance with Thais, willing to sacrifice his own life to secure justice. He begins his training with Chavore that morning. The Legend says that he and Xül were once friends but that they drifted apart because of the enmity between their fathers.

Thatcher’s powers allow him to see people’s circulatory systems and other organs, and Chavore teaches him to apply that ability to plants. Thatcher focuses on a single blade of grass and makes it wither. His mentor is pleased with his progress, and Thatcher resolves to play the part of the perfect pupil to further his goal of killing Olinthar.