Splintered Kingdom by Gretchen Powell Fox

Here is a summary with spoilers for Splintered Kingdom by Gretchen Powell Fox

After surviving the Arcane Crucible, Elyria Lightbreaker returns to Nyrundelle carrying the guilt of killing Evander Ravenswing, her former love, after Varyth Malchior corrupted him. She also blames herself for failing to protect the Crown of Concord, which was stolen by Zephyr, a shapeshifter secretly working for Malchior. Only half of the crown was awarded at the end of the Crucible; the other half remains missing. Elyria intends to hunt down Malchior and recover the stolen piece, but her shadow magic has become difficult to access since she left the Celestial Sanctum. Her relationship with Cedric Thorne also remains unresolved. During the Crucible, Cedric died and Elyria brought him back, leaving them connected by a powerful magical bond even after the original golden thread between them snapped. Meanwhile, Cedric returns to Havensreach with his closest friend, Tristan Hale, and investigates the history of Queen Daephinia, the lost city of Luminaria, and the missing half of the crown. He discovers that historical records offer little useful information and struggles to control a new power within him: flamecalling, a form of magic normally associated with the Arcanians. He conceals this ability from Lord Paramount Leviathan Church, the man who raised him after his parents were murdered.

An unprecedented diplomatic delegation brings Elyria, Kit Ravenswing, Tenebris Nox, Thraigg, and other Arcanians to Kingshelm, the human capital, for the first official visit in more than two centuries. The visit is intended to establish peace between the two realms, but Elyria immediately sees the poverty and inequality throughout the city. While wealthy citizens enjoy magic-powered comforts, impoverished residents in an area known as the Walk struggle with scarce resources and little access to mana. Cedric is equally troubled by the conditions because he has spent time among the city's poorest residents. The Arcanians attend formal celebrations and political meetings, where Elyria is treated as a symbol of peace because she won the Crucible. She dislikes being displayed as a political trophy and clashes with the expectations placed upon her. Cedric and Elyria eventually reunite, and their attraction resurfaces despite their efforts to remain focused on their separate missions. Their magical connection intensifies when they touch, and Elyria's shadows become accessible again. She begins training to control her nightwielder abilities with Nox, learning to shape shadows into weapons and armor. Cedric, meanwhile, continues to struggle with his flamecalling and with the fear that his new magic means he is not entirely human. The two grow closer, but Elyria is reluctant to commit to him because she fears losing someone she loves again.

The political situation deteriorates as Elyria realizes that King Callum and Lord Church are not fully committed to helping her recover the crown. Their access to mana from the Midlands has benefited Havensreach, and they fear that Elyria might use the crown to reunite the divided lands and change the existing balance of power. Cedric begins questioning the motives of the people who raised him and the government he serves. He recognizes that the crown could heal the Chasms separating the realms, allowing both peoples to share the land and resources more fairly. Elyria intends to use the crown's celestial power to restore Arcanis and then destroy the crown so it cannot be abused again, but she has not disclosed the full extent of her plan to either kingdom. As the delegation's stay continues, tensions between the humans and Arcanians rise, and the group faces hostility and prejudice. Cedric and Elyria become more emotionally involved, eventually acknowledging their bond and spending time together privately. However, their responsibilities pull them in different directions. Elyria still wants revenge against Malchior, while Cedric must investigate the missing princess and crown without exposing his own emerging powers. Their friends, including Kit, Nox, and Tristan, become increasingly involved in the political and magical conflicts surrounding them.

Elyria eventually receives a lead on Malchior through Sephone Tempus and Raefe, who have discovered evidence of Cult of Malakar activity near Dawnspire, a settlement close to the Chasm. Elyria, Cedric, Tristan, Thraigg, Jocelyn, Ollie, and others travel together to investigate. The journey forces Cedric and Elyria to spend more time together, although they continue to struggle with the uncertainty surrounding their relationship. Raefe's presence causes additional tension because of his past actions toward Elyria, and Cedric confronts him when he crosses a line. Meanwhile, Cedric begins learning to control his flamecalling with help from Elyria and Sephone. He discovers that he can summon and extinguish fire more reliably by treating his magic as a source of fuel rather than trying to force it into existence. The group reaches Dawnspire and learns that a suspected meeting between Malchior and a mysterious contact named Audaxus has already taken place. They question locals and investigate the trail left behind, but Malchior remains ahead of them. During their travels, Elyria also develops a close bond with Sid, a shadowcat whose connection to darkness complements her own magic.

The investigation eventually leads the group toward Elderglade, the secluded sylvan settlement known for its powerful healers. Their journey becomes dangerous as they encounter hostile forces connected to the Cult of Malakar. A violent confrontation involving sanguinagi, or blood mages, leaves several members of the party seriously injured. Sephone loses consciousness, and Thibault suffers injuries severe enough to prevent him from continuing the journey. Young Shep, who has traveled with the group under a human disguise, reveals his true sylvan appearance and uses his healing abilities to help the wounded. The group realizes that their enemies have infiltrated places they had believed safe and that their movements may have been anticipated. They are forced to divide their party, sending some members back toward Kingshelm while others continue toward Elderglade. Elyria remains determined to find Malchior, while Cedric increasingly recognizes that the mission involves more than recovering the crown: the conspiracy reaches into the institutions and relationships that shaped his own life.

As Elyria and Cedric continue investigating the crown's history, they learn more about the mixedborn princess Selenae, the daughter of Queen Daephinia and King Juno, who was believed to have died during Malakar's betrayal. Selenae survived and is connected to the mystery surrounding the missing half of the Crown of Concord. Cedric's research and the clues uncovered during the journey point toward a deeper connection between his own ancestry and the royal family of ancient Arcanis. He also begins to understand that Lord Church has withheld important information about his parents and the circumstances of their deaths. The group reaches Elderglade and encounters the sanctuary's powerful magical protections. Elyria's magic initially triggers a violent response from the enchanted entrance, throwing her from her horse, but the group continues investigating the sanctuary and its connection to the lost crown. The journey strengthens Cedric and Elyria's bond, and they finally acknowledge that their feelings are their own choice rather than merely a consequence of the Crucible or the celestials' plans. They become physically intimate and promise to choose one another despite the dangers ahead.

Kit and Tenny investigate Lord Church's private office and discover evidence that he has been hiding information connected to the sanctuary and the crown. Cedric's suspicions deepen as he realizes that King Callum and Lord Church have been delaying the search for Malchior because they fear losing control over the mana and political advantages gained through the accords. The situation escalates when the Cult of Malakar attacks and the group discovers that Tenny has been taken by her father. She had agreed to go with him to protect others from being killed. The group travels to Seastone, Lord Church's heavily warded estate beside the Chasm, where Cedric grew up. The estate's secrecy and the previously forbidden eastern wing make Cedric reconsider everything he remembers about his childhood. As they search for Tenny, Cedric confronts the truth that Lord Church is not the man he believed him to be. Lord Church is actually Varyth Malchior, the sanguinagi leader he has been hunting, who murdered Cedric's parents and raised him under a false identity.

At Seastone, Malchior reveals that he suspected Cedric was descended from Queen Daephinia and possessed the rare power of a sunbringer. As a child, Cedric manifested golden fire when his parents were murdered, exposing the power Malchior hoped to exploit. Malchior had searched Cedric's family home for information about the crown and later used him to investigate the missing princess and the crown's whereabouts. He also reveals that Tenny is his daughter and uses her golden locket as part of his plans. The locket is actually the missing half of the Crown of Concord, concealed in the form of a necklace and connected to Cedric's heritage. When Cedric touches it, the crown's original markings reappear, and he realizes that Malchior has possessed the relic without understanding its true nature. Malchior uses blood magic and the estate's manaforge to restrain Cedric and Elyria, intending to sacrifice Cedric and reclaim the ancient darkness associated with Malakar. He explains that Malakar's power was scattered rather than destroyed when Queen Daephinia sacrificed herself to stop him. Malchior plans to reunite that darkness with Daephinia's light and claim dominion over Arcanis.

Elyria breaks free when the light of her bond with Cedric ignites her wild magic and shadows, allowing her to attack Malchior and interrupt the sacrifice. During the struggle, Cedric's blood reaches the manaforge basin, triggering a massive magical eruption that destroys the runes, wards, and much of the tower. Cedric's sunbringer power returns in full, and he fights Malchior with his father's sword, Ashrender. He rejects Malchior's offer of shared power and kills him with a blast of golden fire that burns through his body and shadow magic. Elyria returns to Cedric, and they recover the locket containing the missing crown piece. However, as the group gathers around Malchior's body, his remains begin transforming into a mass of living darkness. Malakar has been resurrected through the power Malchior gathered, and he emerges as a being distinct from Malchior but carrying his face and ancient darkness. Elyria attempts to fight him, but Malakar takes control of her shadows and strips away her ability to wield them. She offers herself in exchange for the safety of Cedric and the others, but Malakar takes her anyway, severing her wings and leaving them behind in a pool of blood. Cedric is left with Elyria's severed wings and the crown's recovered half. Although the magical bond between them remains intact, Elyria is gone, and Cedric vows to bring her back, believing the Crown of Concord can banish Malakar as it did before.