The Marauder’s Map reveals Hogwarts corridors and people in J.K. Rowling’s Harry Potter series.
The map was created by four Hogwarts students who called themselves the Marauders: Remus Lupin, Peter Pettigrew, Sirius Black and James Potter. Their magical aliases were Moony, Wormtail, Padfoot and Prongs. The map shows the school’s rooms and passages, including routes that are difficult or impossible to discover by ordinary navigation.
Fred and George Weasley acquire it from Argus Filch’s confiscated-items cabinet and later give it to Harry Potter. It opens when addressed with the phrase “I solemnly swear that I am up to no good” and closes with “Mischief managed.”
The map’s apparent ability to identify people is especially important because it can expose hidden identities. Peter Pettigrew’s presence at Hogwarts is visible to the map, even though he is disguised as Ron’s pet rat.