The Empty Coffin Substitute

Deep in the mountains of western Hunan lies a 'Death Substitute Gully,' where villagers have for generations practiced a dark trade known as 'substitute living.' This involves using a living person's flesh and blood to nurture a 'substitute body' that will die in place of its original. The gully has an iron rule: anyone who enters must find and destroy their own substitute within seven days, or at sunset on the seventh day, the substitute will claim their life. — Description from novelcodex.org