An He Zhuan

The Dark River, capable of assassinating royalty and nobility in the court and wiping out powerful sects in the wild, is the most feared organization of assassins in the martial world. However, the Patriarch, the leader of the Dark River, is aging and gradually losing control over the organization. During a mission to kill the Second Master of the Tang Clan, the Patriarch is severely injured. Several faction leaders within the Dark River send out assassins, attempting to kill the Patriarch, while the Patriarch seeks out physicians to prolong his life. This race against time, concerning life and death and the future of the assassin organization, begins. Fate brings two young men, who crawled out of the piles of corpses and share a deep bond, to stand on opposite sides…

This is also a prequel novel but is set after Shao Nian Bai Ma, approximately 8 years before the start of Shao Nian Ge Xing.