Devouring Soul, Burning Heaven: Rise of the Blood Slave from the Mass Grave

Mercenary Ye Jin, betrayed by his comrades and killed, transmigrates to the Canglan Continent, waking up as a blood slave awaiting death in a mass grave. The Xuan Yin Sect raises blood slaves, extracting their essence blood to refine pills, treating countless lowly lives as nothing. At the brink of death, the ancient forbidden technique, the Devouring Soul Burning Heaven Art, awakens. Swallowing essence blood, devouring spiritual power, seizing souls—killing becomes his cultivation. Surviving amidst corpses on a rainy night, he kills sect disciples and devours the remnant soul of a three-hundred-year-old demon, gaining the complete demonic art and sect secrets. He disguises himself to survive, returning to the perilous blood slave camp, secretly recording all grievances. The righteous are hypocritical, the demonic ferocious. Crawling out from a sea of blood and mountains of corpses, Ye Jin will use his demonic art to settle blood debts, rise step by step, and carve a path of slaughter to burn heaven and defy the way. — Description from novelcodex.org