Dark Soul

The souls of humans who were driven to death's door by devils. There are many devils in this world who enjoy watching humans suffer. It's not rare to hear tales of them enticing men into unfavorable contracts, offering promises of wealth and power and great magics, only to eventually claim these victims' lives. The unhappy souls of these victims are what spawns these monsters, and they chase the living to assuage the regrets and pain that they can no longer escape from.