Room of Requirement

The Room of Requirement is a room in Hogwarts that only appears when a person is in great need of it. The room then transforms itself into whatever the witch or wizard needs it to be at that moment. It is believed that the room is Unplottable, as it does not appear on the Marauder's Map, nor do its occupants, although this could simply be because James Potter, Remus Lupin, Sirius Black, and Peter Pettigrew never found the room.

Location
The room is located on the seventh floor of Hogwarts castle, and has a hidden entrance opposite the tapestry depicting the attempt of Barnabas the Barmy to teach trolls ballet. The way to open the room is to walk past it three times thinking about what you need and the door will appear.

It is advised that the users of this room be very specific about what they are looking for, as it has been shown that other people can enter the room and see what the occupant is doing if they know how the room is being used. The Inquisitorial Squad found the hideout of the D.A. in 1996 by knowing that the D.A. was in the room at the time. Neville Longbottom used this knowledge to create his hideout, as he specifically asked that the hideout be made unavailable to those who supported the Carrows.

History of Use
The first mention of this room was in 1994, when Albus Dumbledore told Igor Karkaroff of his discovery of a room full of chamber pots when he needed to go to the toilet. However, he was unable to find the room again later.

Dumbledore's Army


In 1995, Harry Potter asked Dobby if he knew of a place where Dumbledore's Army could safely meet. Dobby told Harry of what the house-elves called the "Come and Go Room", or "Room of Requirement", which he had used to treat Winky after she had gotten drunk on Butterbeer, as the room filled with antidotes to butterbeer and an elf-sized bed for Winky to sleep off her inebriation. He also said that Argus Filch had found extra cleaning supplies in the room. During the first D.A. meeting, Fred and George Weasley revealed that it had once taken the form of a broom cupboard which they had used to hide from Filch.

Harry and Dumbledore's Army used the room as their headquarters and practice area. Among the items provided by the room for the D.A. were Dark Detectors and shelves of helpful books such as A Compendium of Common Cures, The Dark Arts Outsmarted, Self-Defensive Spellwork, and Jinxes for the Jinxed. They were eventually discovered by the Inquisitorial Squad.

Room of Hidden Things
Harry used the room again in his sixth year to hide his copy of the Half-Blood Prince's Potions textbook from Professor Snape. He found that many other students had used the room to hide a multitude of other objects, including the Vanishing Cabinet. Inside the cabinet in which he hid the book, Harry found a cage that contained the skeleton of something that had 5 legs.

Also in Harry's sixth year, Professor Trelawney attemped to use the room to hide her sherry bottles, but Draco Malfoy threw her out. Draco was using the room to repair the Vanishing Cabinet so he could smuggle Death Eaters into the castle via a matching Vanishing Cabinet in Borgin and Burkes.

Second Wizarding War
In the 1997-1998 school year, Neville Longbottom and several other students used the room as a hideout to escape the wrath of the new Death Eater professors, the Carrows. The hideout connected to the Hog's Head pub, allowing members of the Order of the Phoenix to enter the school to help fight off Lord Voldemort's attack.

Later that same year, during the Battle of Hogwarts, Harry realised that Rowena Ravenclaw's Diadem, one of Voldemort's Horcruxes, was hidden in the room, as he has seen it in his sixth year while hiding his Potions book; he had even picked it up without realizing what it was. He, Hermione and Ron managed to find it, but were ambushed by Draco Malfoy, Vincent Crabbe and Gregory Goyle. Crabbe let loose cursed fire that destroyed the Horcrux and many other objects, killing himself in the process.

Items Hidden Inside
Harry Potter saw many things that other students had hidden in the room, including:
 * Broken and damaged furniture, perhaps hidden to hide mishandled magic
 * Thousands and thousands of books, probably banned, graffitied, or stolen
 * Winged catapults
 * Fanged Frisbees
 * Chipped bottles of congealed potions,
 * Corked bottles whose contents still shimmered evilly
 * What looked like dragon eggshells
 * Several rusting swords
 * A heavy, bloodstained axe
 * An enormous stuffed troll
 * The broken Vanishing Cabinet that Montague had gotten lost in during the previous school year
 * Hats, jewels, and cloaks
 * A cage with a quintaped skeleton
 * The lost diadem of Ravenclaw, made into a Horcrux
 * The Half-Blood Prince's copy of Advanced Potion Making
 * A chipped old bust of an ugly warlock

Appearances

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

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