To ensure the success of his coup, he orders the assassination of every member of the Royal Cabal, all of whom utter the same mysterious phrase as they are killed: "You can't break Kresimir's Promise".

Concerned about what this could mean, Tamas summons Adamat, a former soldier and police inspector who is now a private investigator, to the Skyline Palace in the center of the capital city of Adopest, as the coup is unfolding.

The next day, Manhouch, his queen and many of the arrested nobles are executed by guillotine, ending the monarchy in Adro and leading the country on the path to civil war.

Adamat conducts his investigation while also dealing with his own issues; his attempt to start a printing press business had failed and he had fallen into debt with some dangerous people, reporting to a mysterious employer.

Adamat eventually travels to the South Pike, a large mountain fortress in southern Adro where he meets with the last remaining member of the Royal Cabal, Privileged Borbador.

Both Adamat and Tamas believe the story to be a myth, but Borbador reveals that a curse was placed on the Cabals to ensure that, if their king was killed, they would be compelled to destroy his killer.

She is stopped by Olem, who has been chosen as Tamas's bodyguard (due to his ability to go without sleep), and reveals that Jakob is still alive and will be sent to the countryside to be raised unaware of his claim to the vacant throne.

Manhouch had been preparing to sign accords with Kez, effectively turning Adro into a vassal state in exchange for gold to pay off his mounting debts.

Sometime after the failed negotiation, a Warden (a human mutated by magic and used by the Kez as bodyguards for their Privileged) unsuccessfully attempts to assassinate Tamas in the secret lair beneath the Skyline Palace where he and his co-conspirators had planned the coup.

Shortly after the confrontation, the group find the Kez army marching on South Pike, its Royal Cabal coming to assist Julene in reaching its peak where they will summon Kresimir.

"[7] Publishers Weekly, gave the book a generally positive review, stating "McClellan neatly mixes intrigue and action..."[8] In 2014, Promise of Blood won the Morningstar Award for Best Fantasy Newcomer.