The Marauder's Map is a magical map from the Harry Potter series created by four Hogwarts students: James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew. It shows the entire layout of Hogwarts School of Witchcraft and Wizardry, including secret passages and the locations of people within the castle. The map is activated by the phrase "I solemnly swear that I am up to no good." The map is notable for its ability to reveal the movements of individuals, represented as dots with their names. It is a key tool for the characters, particularly for Harry Potter, as it helps them navigate the school and avoid detection. The map also has a playful side, as it can be used for mischief and adventure.