Vows of Marble and Blood. The Gilded Republic, #5

Book 5: Vows of Marble and Blood the narrative shifts to the most cynical member of the family, Tiberius, a man who has spent years as the Augusta's primary enforcer, cleaning up the scandals and "disappearing" the problems of his siblings. His cold efficiency is challenged when he is forced into a strategic, high-profile marriage of state with Claudia, the daughter of the family's greatest political rival, a woman who is just as ruthless and strategically minded as he is.
The union is intended to end a generational blood feud that threatens to tear the Senate apart, but the wedding preparations become a literal minefield of assassination attempts and poisoned gifts orchestrated by a third party who wants both families destroyed. Tiberius and Claudia enter the marriage with the intent to spy on one another, but they soon realize that they are the only two people in Rome they can actually trust as the city's political stability begins to collapse.
The story centers on the transition from a "marriage of convenience" to a genuine, formidable partnership where the couple must combine their dark talents to hunt down a common enemy hiding within the Imperial court. As the wedding feast approaches, the marble halls of their new estate become a fortress where their vows are signed not just in ink, but in the blood of those who underestimated their combined power.