The White Reaper : Chronicles of Bai Qi
Before he was General Bai Qi—the "Human Butcher" who buried four hundred thousand men alive—he was a nameless, illiterate stray killing for scraps in a subterranean bandit pit. He had no lineage, only a terrifyingly analytical brain that treated human slaughter like a cold math equation of angles, weight, and friction.
Everything changes the day Prince Sho is thrown into the same mud hole.
Stripped of his royalty by a treacherous brother, Sho has a vision for the throne of Qin, but lacks the teeth to survive the dirt. In the stinking straw, the two teenagers strike a desperate trade: Ink for blood. Sho teaches the feral prodigy how to read maps, manage grain logistics, and see the grand geography of an empire. In return, the stray keeps the prince alive, transforming a handful of broken cellmates into a hyper-precise vanguard that cuts its way out of the cave.
Once free, the real calculation begins. Sho quickly launches a brutal political blitz to seize his stolen crown, while his stray takes the field as his ultimate weapon. For the next forty years, King Sho manipulates the courts of China, while Bai Qi treats massive battlefields like that original prison pit, out-calculating aristocratic armies until the ultimate, horrific slaughter at Changping.
The high court wanted a dead prince. Instead, they unleashed the Reaper.