Pisachas are also known as vetala, and they take the form of ghosts, goblins and vampires that haunt cemeteries and ruins. They are hostile spirits of the dead whose children did not perform funerary rites in their memory. As a result they are trapped in the twilight zone between life and after-life. They make their displeasure known by troubling humans. They can drive people mad, kill children and cause miscarriages.
These creatures can be appeased with gifts or frightened them away with spells. One can free them from their ghostly existence by performing their funerary rites.
Being spirits, unfettered by the laws of space and time, they have an uncanny knowledge about the past, present and future and a deep insight into human nature. Hence, many sorcerers seek to capture them and turn them into slaves.
A sorcerer once asked King Vikramaditya to capture a vetala who lived in a tree that stood in the middle of a crematorium. The only way to do that was by keeping silent.
However, every time Vikramaditya caught the ghost, the ghost would enchant the king with a story that would end with a question. No matter how hard he tried, Vikramaditya would not be able to resist answering the question. This would enable the vetala to escape and return to his tree. The stories of the vetala have been compiled in the book “Vetala-pachisi”.