The Pillownomicon

The Pillownomicon first appeared in the episode "Puhoy".Quilton says to Finn  that the book was retreived from the catacombs of the Pillow People. The Pillownomicon reveals that the door through which Finn entered the Pillow World appears randomly throughout time. The only information in the book revealed is about the door.

Trivia

 * The name of the book is a reference to H.P. Lovecraft's Necronomicon.