I Transmigrated as a Divine Trickster System

Others transmigrate and get a system; I transmigrated and became the system. No body, no magic, just a head full of modern knowledge, bound to a clueless passerby. I trick him into playing a divine trickster: making ice with saltpeter, catching ghosts with phosphorescent fire, fooling the Tang Dynasty with science. The trickster is fake, but unifying the Tang and making the Xiongnu Khan call me Father—that must be real. — Description from novelcodex.org