In Hindu mythology, the Pretas are the spirits of dead people that inhabit Preta-Loka, the realm of tortured spirits. These are the spirits that had committed wrongful deeds in a former life and have been committed to the circle of perpetual hunger. Some are said to animate dead bodies and inhabit graveyards. In total, there are thirty-six classes of Pretas, some only appearing as animated skeletons.
The Japanese equivalents of the Pretas are the Gaki, the hungry ghosts. Invisible to humans in their real form, they can assume any shape. They are depicted as footless beings with wide mouths and swollen bellies.