The Marauder's Map

The Marauder's Map is a magical map of Hogwarts. It shows the people inside the castle in miniscule figures, labeled with their names. It also gives information on how to open secret passageways, though several locations (such as the Room of Requirement and the Chamber of Secrets) do not appear on the map. The map was created by the four students known collectively as "The Marauders", who had extensive knowledge about the school grounds, such as its various hidden passages, from their frequent night-time adventures together. These marauders were James Potter (Prongs), Sirius Black (Padfoot), Remus Lupin (Moony), and Peter Pettigrew (Wormtail). At first glance, the Map is simply a blank piece of parchment; but when the user points their wand to the Map and says, "I solemnly swear that I am up to no good," the message "Messrs Moony, Wormtail, Padfoot and Prongs, purveyors of aids to magical mischief-makers, are proud to present the Marauders Map," and a detailed layout of Hogwarts' Castle is revealed. Saying, "Mischief managed!" returns the map to its original blank state. In Harry Potter and the Prisioner of Azkaban, Fred and George (who have no further need for it) give the Map to Harry so he can get to Hogsmeade Village through a hidden passageway and tell him they had stolen it from Filch's office a few years ago.