Reiki

Reiki (Japanese: 霊鬼 or れいき, meaning "ogre spirit" or "demon ghost") are the ghosts of oni unable to pass on to the afterlife in Japanese mythology.

Myths & Legends
Though some oni can be killed by man-made weapons and others die of natural causes, they do not always peacefully pass on to the next life. Some still have unfinished business or karma left to burn off, while others die such violent or passionate deaths that the soul becomes disjointed at the moment of death and they remain in the human world as a demon ghost.

There are fewer stories about reiki than about oni, but the stories that exist tell of powerful spirits even more fearsome than their living counterparts. One of the most well-known reiki legends takes place at Gangō-ji, a temple in Nara. A mysterious force was haunting the temple’s bell tower and murdering children every night. The force was so powerful that not even the most powerful priests could identify it, let alone exorcise it. In a story reminiscent of the adventures of Hercules, only the son of a god was strong enough to track down and defeat the demon ghost, saving the children of the temple.

Appearance
Reiki appear as they did before death, though they are often accompanied by an aura or an eerie glow. They are semi-transparent like ghosts, and they often gain additional supernatural powers in addition to the magic they knew in life.

Behavior
Reiki have only one motivation: revenge. They seek to bring suffering to the person or people they feel are responsible for their death, or to those who stood against them in life. They can haunt for centuries, following a target, or else attaching themselves to a particular area – often their own grave site – and assaulting those who come near. These hauntings usually persist until exorcised by a powerful Buddhist priest.