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Harry Potter Wiki

The Underground Chambers[2] were a series of rooms below Hogwarts School of Witchcraft and Wizardry, serving as the defences protecting the Philosopher's Stone from 1 August, 1991 until 4 June, 1992.[1] There were a total of seven chambers, each of which containing an obstacle or task that guarded the Stone and delayed any intruder.[1]


In 1991, the Philosopher's Stone became the target of Lord Voldemort due to its potent ability to return him to full power. Suspecting danger, Albus Dumbledore set out Rubeus Hagrid to retrieve the Stone from Vault 713 at Gringotts Wizarding Bank the same day he took Harry Potter to Diagon Alley. That same day, Quirinus Quirrell, who was being used as the parasitic host of Lord Voldemort, broke into the bank, but failed to obtain the Stone.[1]

Thereafter, Hagrid brought the Stone to Hogwarts as requested, and Professors Pomona Sprout, Filius Flitwick, Minerva McGonagall, Quirinus Quirrell and Severus Snape, as well as Hagrid and Dumbledore themselves, each created their own separate chamber.[1]


Order of encounter

Obstacle (Preparer)


Fluffy (Rubeus Hagrid) Fluffy PM B1C9M3 ForbiddenCorridorFluffy Moment.jpg

The only known way to access the Stone was through a trapdoor in the Third-floor corridor, which was guarded by the three-headed dog Fluffy. To get past this obstacle, one had only to play some music, which would then put Fluffy to sleep.[1]

Devil's Snare (Pomona Sprout) Devil.JPG

Through the trapdoor and a long and dark drop through the air, led into a chamber full of Devil's Snare. The plant was designed to entangle and suffocate any intruders, especially quickly the more the intruder tries to escape. Bluebell Flames, however, could be used to scorch them.[1]

Winged Keys (Filius Flitwick) B1C16M1.jpg

A downwards sloping passage with stone walls, through which trickling water could be heard, led to a brilliantly lit chamber with a very high ceiling, full of glittering winged keys. On the opposite end of the chamber from the stone passage was a large, old-fashioned wooden door with a silver lock that would not open, even with the Alohomora Charm, without the necessary key. One had to mount a broom and attempt to pursue the correct key; all of the keys fluttered away quickly, darting around, making it very difficult to catch the correct one.[1]

Chessboard Chamber
(Minerva McGonagall) B1C16M2 Chessboard Chamber.png

"I think we're going to have to be chessmen."
— Ron[src]
This chamber was so dark that it was impossible to see anything. It contained a Human Chess Game. To get across the chamber, one had to checkmate the King according to the rules of Wizard's Chess.[1]

Mountain troll (Quirinus Quirrell) Trollps1.jpg

"I do say I have a gift with trolls."
— Quirrell discussing his chamber[src]
A chamber containing a mountain troll at the entrance; it had a foul odour in it, and it was said that there was great relief in passing through it.[1]

Potion riddle (Severus Snape) Potions Riddle.png

Upon entering the chamber, the entrance was blocked by purple flames, whilst the exit was covered by black flames. A table holding seven unlabelled potion bottles of differing shapes and sizes sat in the centre of the room, with a logical riddle. Three were poison, two contained nettle wine, one contained a potion to safely traverse the black flame, and the last contained a potion that allowed passage back through the purple flames. The riddle, when properly worked out, revealed the contents of each bottle, and therefore which one was safe to drink to allow onward progress.[1]

Mirror of Erised (Albus Dumbledore) Quirrell and Harry by the Mirror of Erised.png

"You see... Only a person who wanted to find the stone. Find it, but not use it, would be able to get it."
— Albus Dumbledore[src]
The chamber contained the Mirror of Erised. The only way to obtain the stone was for an individual to look into the mirror and see themselves possessing the stone but not using it.[3]

Behind the scenes

  • The prevalence of the number seven is not coincidental; seven obstacles were in place to get to the Philosopher's Stone and seven different potions were available in Snape's logic riddle. Seven, as deduced by Arithmancer Bridget Wenlock, has magical properties to it. It is believed that the number seven is the most magical number. It is also, of course, the total number of books in the series, (with Rowling firmly sticking to that number), and the number of pieces Voldemort desired his soul to be in (as he recognised the significance of the number seven and believed it to be the greatest).
  • The fifth and sixth obstacles were cut from the film adaptation of Harry Potter and the Philosopher's Stone. The potion riddle, however, was later shown in the second disc.


Notes and references

Hogwarts Castle
Locations below ground floor

Boathouse · Chamber of Secrets · Conical Crypt · Dark Hall · Deathday Party Hall · Defence Against the Dark Arts dungeon · Dungeons · Dungeon cave · Dungeon Five · Dungeon hall · Dungeon Pit · Entrance Dungeon · Forgotten Cavern · Hieroglyphic Hall · Hogwarts Basement · Hufflepuff Basement · Kitchens · Lever Rooms · Porticus Circumscriptus · Porticus Periculum · Porticus Imago · Porticus Medius · Potion-Mixing Room · Potions basement · Potions Classroom · Quidditch cave · Room of Doom · Room of Runes · Severus Snape's office · Shop · Slug Pit · Slytherin Boys' Dormitory · Slytherin Duelling Dungeon · Slytherin Dungeon · Slytherin Girls' Dormitory · Underground Chambers · Vestibule of Mischief

Paths and staircases

Boathouse passageway · Corridor of Secrets · Detention escape route · Dungeon Corridor · Dungeon Staircase · Lost Tunnel · Lower Chambers Corridor North-East · Lower Chambers Corridor West · Lower Chambers Portrait Corridor · Poltergeist Passage · Prowling Passage · Slughorn's Stairs · Undercover route to the Kitchens · Way to Courtyard

Portraits, statues and other artwork located below ground floor

Basil Fronsac · Bloody Baron · Cecilia Gallerani · Elizabeth Burke · Hooky · Mad old man · Mopsus · Old man · Percival Pratt · Salazar Slytherin · Sleeping hermit · Bearded man with book