Marauder's Map

"Messrs. Moony, Wormtail, Padfoot, and Prongs Purveyors of Aids to Magical Mischief-Makers are proud to present THE MARAUDER'S MAP"

- The Marauder's Map

The Marauder's Map is a magical parchment that reveals all of Hogwarts School of Witchcraft and Wizardry. Not only does it show every classroom, every hallway, every corner of the castle, but it also shows every inch of the grounds, as well as all the secret passages that are hidden within its walls.

More importantly than that, the Map shows every single person who is within the boundaries of Hogwarts grounds as small black, labeled dots showing, "where they are, what they are doing, every minute of every day.", even when the people are transformed animagi, wearing an Invisibility Cloak, or under the influence of the polyjuice potion, as demonstrated when Remus Lupin saw Harry Potter, Ron Weasley and Hermione Granger sneaking to Hagrid's house under an Invisibility Cloak.

The Marauder's Map was created by Remus Lupin (Moony), Peter Pettigrew (Wormtail), Sirius Black (Padfoot), and James Potter (Prongs) while they were attending Hogwarts. The titles on the map refer to these four men in their animagi forms, respectively. This artifact proved quite useful to the foursome (commonly termed Marauders) through the years, though at some point, Argus Filch confiscated it. Fred and George Weasley "nicked" it from his office in their first year at Hogwarts, and later gave it to Harry Potter in his third year.

The map is normally disguised as a blank piece of parchment. To view the map, one must tap it with one's wand and recite, "I solemnly swear that I am up to no good." The content of the map will reveal itself.

To hide the contents of the map so the parchment appears blank again, one must again tap it and recite, "Mischief managed."

If someone tries to view the map without reciting the proper incantation, the map merely insults them and tells them to mind their own business. Severus Snape experienced this phenomenon when he tried to view the map by force.

An added bonus is that if the bearer of the map approaches the entrance to a secret passage protected by a password, the password will appear on the map.

Barty Crouch, Jr., disguised as Professor Mad-Eye Moody once took the map from Harry, but after Crouch was unmasked, he reclaimed it.

Harry uses the Map throughout his time as a student at Hogwarts, especially during his third year, when he tried to find his way into Hogsmeade, and during his sixth year when he spent a great deal of time obsessing over Draco Malfoy's daily activities.

When monitoring Draco Malfoy, Harry found he often disappeared off the map. The cause of this was not revealed until after he asked Dobby to trail Draco to find out what he was doing when disappeared off the map. When Dobby told Harry he disappeared into the Room of Requirement, which was not on the Marauder's Map. Whether because it was Unplottable or the marauders never found the room was unspecified.

According to J.K. Rowling, Harry never gave the map to any of his children, but James Potter II probably snuck it from Harry's desk.

Plot Hole?
The magical defenses on Hogwarts have been mentioned several times, including Hogwarts being unplottable. That is it should be impossible to map Hogwarts, which is exactly what the Marauder's Map does. There are some possible loop holes for this, for example making a place unplottable might simply make it impossible for it to be mapped with reference to somewhere else, while the Marauder's Map is simply a map of Hogwarts, not of its position relative to (for example) London.

Behind the scenes
There is a toy version of The Map within every Harry Potter and The Order Of The Phoenix Videogame which is an exact replica of the in-game Map.

Appearances

 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (film)
 * Harry Potter and the Prisoner of Azkaban (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows