The day before the Christmas holiday, Harry and his friends are investigating the identity of Nicolas Flamel in the Hogwarts library, "because how else were they going to find out what Snape was trying to steal?" Their research is interrupted, however, by the librarian, Madam Pince. Harry and Ron promise Hermione that they will keep researching during the break; she, for her part, is going home for the holiday. Once vacation begins, however, the boys have "too good a time to think much about Flamel," including games of wizard chess, in which the chess pieces are alive. On Christmas morning, Harry awakes to discover that he has received presents, one of which is a cloak that turns its wearer invisible. An anonymous note with the cloak claims that the garment belonged to Harry's father, and admonishes Harry to use it well. After a wonderful Christmas feast, Harry uses the Invisibility Cloak to enter the Restricted Section of the library. He opens one book only to hear it screaming, alerting Filch to his presence in the stacks. Harry evades the caretaker-who has informed Professor Snape that someone has been trespassing in the Restricted Section-and enters an unused classroom. In the room stands a tall mirror, at the top of which is carved: Erised stra ehru oyt ube cafru oyt on wohsi. (Read the inscription backward and adjust the spaces between the words.) When Harry peers into the mirror, he sees himself surrounded by several others not in the room with him. He intuitively recognizes two of the others as his parents. The next night, with Ron hiding under the Invisibility Cloak alongside him, Harry returns to the mirror room. While Harry again sees his family in the mirror, Ron sees himself as head boy at Hogwarts and captain of the Quidditch team. Although Ron urges him not to, Harry returns to the mirror room a third night. Dumbledore is waiting for him. He explains to Harry that the mirror shows those who look into it "the deepest, most desperate desire of [their] hearts." He warns Harry, "I ask you not to go looking for [the mirror] again . . . . It does not do to dwell on dreams and forget to live . . . ."
In stories of heroic quests, heroes must often face tests or challenges that threaten the quest's successful outcome. The Mirror of Erised (again, read backward) is one such potential trap for Harry. The fact that the mirror reveals to its gazers their "most desperate desires" makes it a particularly treacherous obstacle, for, as Dumbledore suggests, human beings often are content to dwell on what is not rather than what is. As mythology scholar Joseph Campbell states, "When you follow the path of your desire and enthusiasm and emotion, keep your mind in control, and don't let it pull you compulsively into disaster" (The Power of Myth, p. 132). In effect, Dumbledore-clearly serving in this moment as the hero's mentor-offers Harry the same wisdom.