Wayang Kulit is an Indonesian magic book that allows the user to manipulate everything related to shadows, including but not limitated to, summoning and controling supernatural beings, deep levels of telepathy, umbreokinesis (shadow manipulation) and so on. The supernatural beings that can be summoned and controlled include ghosts and shadow creatures, though the guardian used normal human beings in black slinkys because they are far easer to control. The only limitation of the book is that the user must be able to read and speak the Indonesian language the book is written in.
During the Wayang Kulit chapter, Bun-bun attempt to find the book in order to summon and get revenge against the groundhog's shadow for ruining his plans and forcing him to wander for years in the Timeless Space. After a long mental battle with Torg and Kiki, Bun-bun succeds in getting the book, but to his dismay, he soon finds out that he need to speak indonesian to use the book, destroying any change of getting revenge against the shadow.
It's not know why Bun-bun tried to summon the Groundhog's Shadow with that book regarding that he can do it with the Book of E-Ville, though it's to be notice that Bun-bun wanted revenge against the shadow for forcing him to give-up his holidays powers, but he couldn't physically strike him, so he needed of book specialized in the manipulation of shadows to get his revenge. Unable even to read the book, Bun-bun got mad and threw the book down. It's current location is unknown.