Mass Grave Shared Rental

There are 7 resentful spirits in a mass grave. People from two different worlds accepted the mission for different reasons. The mission is: to eliminate the grievances of the resentful spirits. How did the deceased in the mass graves die, and what kind of grievances do they have? Stay tuned Overhead modern fantasy suspense Concept: There may not necessarily be ghosts in mass graves, but there must be ghosts in the world