In the shadowy depths of the palace in the seventeenth year of Yonghui, a tale of bloodlines, power struggles, and flashing blades slowly unfolds. Gu Ren, an orphan from the Xuanjia Workshop, infiltrates the Office of Palace Affairs to avenge his murdered family. Amid the bloody haze, he discovers that his younger brother, Li Gou'er, has been made the “blood catalyst” for the Blood Butcher Blade. Meanwhile, Qingyuan, a palace maid from the Cold Palace, emerges with a treasured relic of the Ironblood Alliance. The two are drawn into a royal conspiracy by fragments of the Stop the War Sword: Consort Shu has used a cat to replace a prince to conceal her childlessness, while the Imperial Arsenal sacrifices boys' blood to forge an evil blade, hoping to control the realm in the name of the “chosen prince.”
The clash between mechanical arts and blade-forging runs throughout the story: the magnetic gears of the puppet Night Owl, the secret-fire tempering of the Ironblood Alliance's Immortal-Binding Thread, and the bloodline resonance of the Seven Constellations of the Black Tortoise formation together create a strange world of courtly intrigue and martial arts. The birthmarks of the twins correspond to a star chart, Qingyuan's blindness conceals the power to see through illusions, and the fragment of the Ironblood Token protected by Consort Xian in the Cold Palace all point to the “Stop the War” pact between the Xuanjia Workshop and the Ironblood Alliance, made three hundred years ago. When the Blood Butcher Blade's unfinished form reveals the flesh and blood of Gu Ren's younger brother in the secret fire, and the phantom of the Stop the War Sword reappears through the resonance of their shared blood, the clash of blades raises a question that goes beyond family vengeance: “A blade is not wrong in itself. The fault lies with the one who wields it.”
The seven-day deadline for the sacrificial ceremony, the secret fire of dragon bones in an underground blood pool holding a thousand people, and the Shadow Guards' interlocking schemes tighten around them like a web. Gu Ren and Qingyuan struggle through mechanical traps and poisonous blood pools. They must solve the bloodline riddle of the Midnight Mandarin Duck Lock while protecting the true royal bloodline amid a whirlpool of power struggles. When the broken blade and the fragments of the Ironblood Token join to form a hilt inscribed “Xuanjia and Ironblood, united to slay evil,” a deadly contest begins, with blood as its blade and peace as its martial way,
