In the seventeenth year of Jian'an, on a bitterly cold night, a blood moon rises over Hanging Coffin Gorge.
Shen Yanzhi, deputy commissioner of the Black Armor Guard, is investigating a smuggling case involving illicit salt when he is drawn into a struggle over the "Reverse Scale" among twelve black sandalwood coffins. The legendary dragon's Reverse Scale, said to be hidden within the Twelve Golden Men, is closely tied to the massacre of the Jingnan Prince's residence and a royal conspiracy over the succession. He crosses paths with Xiao Yan, a notorious killer from the martial world, and the two are forced by a bronze secret scroll to swear a "Blood Pact," sharing pain and fate.
On the surface, it is a clash between an imperial enforcer and a heretic cultivator. In truth, it is a collision between the fates of twin brothers. Shen Yanzhi bears the blood-soaked legacy of his family's massacre, yet mistakes his enemy for his father and becomes a blade in the hands of the royal family. Xiao Yan has endured three years of humiliation, stirring up the martial world under the name "Blood-Hand Butcher" solely to uncover the truth: the empress slaughtered the entire Jingnan Prince's household to seize the bloodline of the "Dragon-Devouring Gu."
When an army of living terracotta warriors emerges beneath the ruins of the Jingnan Prince's residence in Jinling, the two discover that every conspiracy points to the ultimate secret of the "Dragon Bone Reverse Scale." Only by bringing together the bloodlines of the twins can its power be awakened, and their sister, Shen Qinghe, Xiao Yan's deceased wife, had willingly sacrificed herself to serve as the "key." A side effect of the Blood Pact causes Shen Yanzhi to keep dreaming of fragments of his sister's death. He realizes that the Black Armor Guard was not responsible for her death: she fell victim to the Heavenly Secrets Pavilion's scheme of using one person to kill another.
As the Crown Prince, the empress, and the Heavenly Secrets Pavilion converge on Jinling, Shen Yanzhi and Xiao Yan are forced to choose between "loyalty to the court" and "revenge for their kin." The red thread of the Blood Pact tightens ever more. One wants to destroy the Reverse Scale and put an end to the royal family's ambitions; the other wants to wield it and reshape the order of the martial world. Yet when they cross swords, they discover the "Reverse Scale" birthmarks on each other's palms. They are the true "Dragon Bone vessels," and their sister gave her life...
