A Monsoon Rising by Thea Guanzon

Here is a summary with spoilers of  A Monsoon Rising by Thea Guanzon

After their political marriage, Alaric and Talasyn remain wary of one another despite being forced to rule together. Talasyn is crowned Night Empress, but her coronation is interrupted when Sardovian rebels attack the citadel in an attempt to assassinate her. During the fighting, Alaric protects Talasyn, and she later saves his life in return. The attack forces them to publicly present a united front while privately questioning one another's loyalties. Alaric's decision to protect Talasyn earns the disapproval of Regent Gaheris, who later subjects his son to another round of torture through the Shadowgate as punishment for placing Talasyn above the Night Empire's interests.

Although they begin cooperating in public, both continue pursuing separate agendas. Gaheris orders Alaric to help Talasyn master the combined use of Lightweaver and Shadowforged magic so they can stop the approaching World Eater, but instructs him to strip Talasyn of her Lightweaver abilities afterward. At the same time, Talasyn and members of her council quietly discuss eliminating both Gaheris and Alaric once the greater threat has passed, believing it is the only way to secure Nenavar's future. Meanwhile, Talasyn investigates the visions she experiences through the Light Sever, uncovering more about her mother, her royal heritage, and the ancient connection between the Lightweavers and the coming catastrophe.

As the Seven Moon Eclipse draws nearer, Alaric and Talasyn devote themselves to combining their opposing magics into a stable force capable of resisting the Voidfell and destroying the World Eater. Their training repeatedly fails before they slowly learn to synchronize their powers. During this time they spend periods apart, exchanging letters while fulfilling separate political obligations. Alaric returns to Kesath to deal with Gaheris and the imperial court, while Talasyn remains in Nenavar continuing her research and preparations for the coming eclipse.

Alaric later travels to Talasyn's island to resume their magical training. While exploring the Mouth of Night, the pair are trapped together by a powerful monsoon that prevents them from leaving for several days. Isolated from their courts, they discuss their pasts, their experiences during the Hurricane Wars, and the burdens placed upon them by their families and kingdoms. During this time they begin a physical relationship, agreeing that it does not change the political nature of their marriage. Once the storm passes, Alaric returns to the Dominion while Talasyn continues preparing for the eclipse.

When the Seven Moon Eclipse begins, Alaric and Talasyn reunite to confront the awakening World Eater. Using the combined power of light and shadow, they successfully forge the magical force needed to contain and defeat the ancient threat before it can consume the world. The victory comes at a significant cost. Alaric suffers permanent injuries, including a scar across his face, while Talasyn is left with a permanent scar on her arm from the battle. Although the World Eater is defeated, the effort exhausts both rulers and leaves their kingdoms politically unstable.

Following the victory, celebrations are held while tensions continue to rise beneath the surface. Talasyn struggles to reconcile her growing attachment to Alaric with her long-standing plans to oppose the Night Empire. At the same time, Gaheris's supporters begin putting new plans into motion. During a masquerade celebration, reports emerge of a coordinated prison break organized by the Dominion Court, while unrest spreads through Talasyn's own court. The political situation rapidly deteriorates as multiple conspiracies unfold simultaneously.

The betrayal comes from within Talasyn's closest circle. Oryal, one of her most trusted companions, is revealed to have been working alongside Queen Urduja as part of a larger conspiracy. Oryal uses a substance derived from sariman blood to suppress Talasyn's Lightweaver magic before Talasyn is drugged and abducted. With her powers removed, Talasyn is transported to the Dominion Court as a prisoner. Alaric is unable to prevent her capture and is left separated from her as the novel ends, leaving the alliance between Nenavar and the Night Empire in jeopardy and Talasyn imprisoned without her Lightweaver abilities.