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Underground Chambers

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The Underground Chambers[1] were a series of rooms underneath Hogwarts School of Witchcraft and Wizardry that served as the defences surrounding the Philosopher's Stone in the 1991-1992 school year. There were seven chambers in total that contained an obstacle or task that guarded the stone from being stolen.


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 a parasite of Lord Voldemort broke into the bank, but failed to obtain the stone.

The seven obstacles in the Underground Chambers was then created in Hogwarts School with the intent of protecting the stone.


First obstacle


Rubeus Hagrid's chamber

Ron: "What do they think they're doing, keeping a thing like that locked up in a school?"
Hermione: "You don't use your eyes, do you? Didn't you see what it was standing on?"
Ron: "I wasn't looking at its feet! I was a bit preoccupied with its heads... or maybe you didn't notice? There were three!"
Hermione Granger and Ronald Weasley discussing Fluffy's chamber[src]

The only known access way was from a trapdoor in the Third Floor Corridor, which was guarded by the three-headed dog, Fluffy. This obstacle was set by Rubeus Hagrid. To get past this, one had to "play a bit of music" and put Fluffy to sleep. Fluffy guarded a trap door that leads to the next obstacle. Professor Quirrell most probably enchanted a harp to put Fluffy to sleep while Harry played a wooden flute.


Pomona Sprout's chamber

Second obstacle

Hermione: "Devil's Snare, Devil's Snare... What did Professor Sprout say? It likes the dark and the damp-"
Harry: "So light a fire!"
Hermione: "Yes - of course - but there's no wood!"
— Getting through the Devil's Snare's chamber[src]

After going through the trapdoor, a long drop led to a chamber filled with Devil's Snare, planted by the Herbology teacher, Professor Sprout. The Devil's Snare was designed to entangle and suffocate any intruders, especially quickly the more the intruder attempts to escape. As the Snare is sensitive to heat and light, Hermione used a charm that created a jet of Bluebell flames to free Ron.

Third obstacle

Winged keys 03

Filius Flitwick's chamber

Hermione: "These birds... they can't be here just for decoration."
Harry: "They're not birds! They're keys! Winged keys."
— Harry and Hermione upon entering the chamber of winged keys.[src]

A downward sloping passage led to another chamber filled with flying keys, charmed by Professor Flitwick. A large wooden door led to another chamber. The door would not open with the use of any charm such as Alohomora, one needed the correct key to get through. To pass, one had to use the broomstick provided to catch the correct key. However, once airborne, the other keys will try and attack the pursuer.


Minerva McGonagall's chamber

Fourth obstacle

Ron: "You see it, don't you, Harry? Once I make my move, the Queen will take me. Then you're free to check the King."
Harry: "No. Ron, NO!"
Hermione: "What is it?"
Harry: "He's going to sacrifice himself."
— Harry, Ron and Hermione in the chess chamber[src]

The next chamber was dark and resembled a graveyard, it contained a Human Chess Game, enchanted by Professor McGonagall. To defeat the game, one had to play themselves across the board and checkmate the King according to the rules of Chess. One cannot simply walk across the board and pass, so an adequate knowledge of Wizard's Chess was needed to complete this task.

Quirrell's Obstacle

Quirinus Quirrell's chamber

Fifth obstacle

Hermione: "Go on"
Harry: "I'm glad we didn't have to fight that one, come on, I can't breathe."
— Harry Potter regarding the knocked out Troll[src]

The following chamber contained a Mountain Troll that needed to be defeated in order to pass. This chamber had a terrible smell to it and it was of great relief to Harry and Hermione that they didn't have to be in there too long. This was provided by Professor Quirrell. When Harry and Hermione got there, the troll was already knocked out thanks to Professor Quirrell.

Sixth obstacle

Potions Riddle

Severus Snape's Chamber

Hermione: "This isn't magic - it's logic - a puzzle. A lot of the greatest wizards haven't got an ounce of logic, they'd be stuck in here forever."
Harry: "But so will we, won't we?"
Hermione: "Of course not, everything we need is here on this paper. Seven bottles: three are poison; two are wine; one will get us safely through the black fire and one will get us back through the purple"
— Hermione and Harry discussing the Logic Chamber[src]

The next obstacle guarding the Stone was a logical riddle set by Professor Snape. Upon entering the chamber, the doorway through which one entered was blocked by a purple flame. The other entry way leading to the Philosopher's Stone, was blocked with black flame. A table with seven bottles of differing shapes sat in the middle of the room.

Each bottle contained a liquid, but the bottles were not labelled with their contents. 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:

"Danger lies before you, while safety lies behind,
Two of us will help you, whichever you would find,
One among us seven will let you move ahead,
Another will transport the drinker back instead,
Two among our number hold only nettle wine,
Three of us are killers, waiting hidden in line.
Choose, unless you wish to stay here for evermore,
To help you in your choice, we give you these clues four:
First, however slyly the poison tries to hide
You will always find some on nettle wine's left side;
Second, different are those who stand at either end,
But if you would move onwards neither is your friend;
Third, as you see clearly, all are different size,
Neither dwarf nor giant holds death in their insides;
Fourth, the second left and the second on the right
Are twins once you taste them, though different at first sight." [src]

Based on Hermione's deductions, from left to right, the potions lineup is:

  1. Poison
  2. Nettle wine
  3. Potion to move the drinker forward through black flames
  4. Poison
  5. Poison
  6. Nettle wine
  7. Potion to move the drinker backwards through purple flames

As Professor Quirrell presumably travelled through the chamber to reach the Mirror of Erised, he must have had to take the Black Fire Potion himself, and, as there was only enough potion for one person in the bottle, that would have used it all up. However, he may have taken some of the potion with him when he entered the chambers, and drunk that instead. Another possibility is that the bottles had had a Refilling Charm on them.


Albus Dumbledore's chamber

Seventh obstacle

Harry: "You!"
Quirrell: "Me, I wondered whether I'd be meeting you here, Potter."
— Harry Potter discovering Professor Quirell in the seventh chamber[src]

The final obstacle was the Mirror of Erised, designed and set by Albus Dumbledore. The only way to obtain the stone was to look into the mirror, see yourself having it, but not using it.

Most people would see themselves using it, such as turning things to gold, crafting Elixir of Life, or giving it to someone. This is what Quirrell saw. Harry however, was able to get the Stone because he only wanted to save it and not use it.

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.
  • In the film adaption of Harry Potter and the Philosopher's Stone an Undetectable Extension Charm were possibly put at the Winged Key Chamber, as it was taller than the Devil's Snare Chamber and Fluffy Chamber together, and it could not be seen from the outside of the Hogwarts Castle.
  • The fifth and sixth obstacles were cut from the film. This is curious, as Snape was the one who was suspected to want to steal the stone, and Quirrell was the one who actually wanted to. This is also a bit strange because in the film Hagrid still says that Snape is one of the teachers protecting the stone. However, in the film, when the Trio unlocks the door, a bit of the Troll Chamber can be seen, and the Potion Riddle appears on Disc 2. It is possible that the film makers just cut from the Winged Keys Chamber to the Mirror of Erised Chamber.
  • At one point in the "Battle of Hogwarts" chapter in Deathly Hallows, Hermione asked Ron are you a wizard or not?. This might have been a reference to what was said in the Devil's Snare Chamber by Ron to Hermione, are you a witch or not?.
  • In the original script of Deathly Hallows Fluffy, the first obstacle, was going to participate in the Battle of Hogwarts.
  • In some video games an antechamber to the Mirror of Erised chamber appears, which makes out eight obstacles. However, it is possible that the antechamber is a part of the last chamber.
  • In the PS1 version of Harry Potter and the Philosopher's Stone the Potion Riddle chamber is called You-Know-Who. It is unknown why.
  • There were a lot of differences in the Chambers between the books, films and video games, shown in the following table:
Room Book Film PC Game PS1 Game Pottermore GBC/GBA Game LEGO Years 1-4
Fluffy's Chamber and Through the Trapdoor Harry and then Hermione played the flute Hagrid gave Harry for Christmas. Disc 1: Quirrell bewitched a harp to play itself.
Disc 2: The player has to choose between four items: the Cloak of Invisibility, a chicken, a bone or a flute.
Harry plays the flute Hagrid gave him and has to put all 3 heads asleep at once; the heads will wake up once asleep enough. Harry plays the flute Hagrid gave him. Not seen. Same as PS1. Desktop: When Harry, Ron and Hermione enter the room to see Quirrell climb into the room, when he finds out they have seen him he destroys the playing harp and wakes Fluffy. Ron tries playing a trumpet but it doesn't work. In order to fix the harp they have to distract Fluffy with a rubber duck.
Handheld: When Harry, Ron and Hermione enter the room to see Quirrell climb into the room, when he finds out they have seen him he destroys the playing harp and wakes Fluffy. Ron tries playing a trumpet but it doesn't work. Fluffy then chase Harry through the Third Floor until Harry jumps through the trapdoor.
Devil's Snare The three are grabbed by the Devil's Snare; Hermione defeats it with Bluebell flames. Disc 1: The three are grabbed by the Devil's Snare; Hermione's directions were to relax, after which the plant would release Harry and Ron. However, Ron, being the last one trapped, and being afraid, couldn't calm himself enough leading Hermione to cast Lumos Solem, allowing Ron to slip through.
Disc 2: Not seen.
Only Ron and Hermione are grabbed by the Devil's Snare; Harry defeats it with the Fire-Making Spell. Same as PC. Not seen. GBC: Only Ron and Hermione are grabbed by the Devil's Snare and Harry defeats it in a duel.
GBA: Only Ron and Hermione are grabbed by the Devil's Snare; Harry defeats it by burning it with torches.
Desktop: Only Ron is grabbed by the Devil's Snare; Harry defeats it with the Wand-Lighting Charm.
Handheld: Not seen.
Winged Keys Harry, Ron and Hermione catch the key. Disc 1: Harry catches the key.
Disc 2: You must search and click on the right winged key.
Same as film. Same as film. However, the wrong keys shine red and the right key shine blue and it's wing is not broken. You must search and click on the right winged key. Same as film. Desktop: Same as film, except for the fact that Harry shoot spells at the key.
Handheld: Harry finds the hideout of the key, then same as film.
Giant Chess Board Harry is a bishop, Hermione is a rook, Ron is a Knight and is injured after sacrificing the Knight in order to win. Same as book, except Ron rides the Knight instead of taking its place. Ron defeats most of the pieces and gets injured, Harry defeats the rest, Hermione doesn't play and Harry and Ron need to get the pieces to attack each other, but not attack them. There are three boards; Ron defeats most of the pieces on the first board and gets injured, Harry defeats the rest, Hermione doesn't play. You just see a few pieces move around. GBC: Ron defeats the Queen and gets injured, Harry defeats the rest, Hermione doesn't play.
GBA: Harry paralyses all the pieces on top of the door-opening platforms, realising the lack of pieces to all the platforms, Ron stays on top of the last one.
Desktop: After directing the pieces on the board where to move and winning, Ron trips over the King's sword and watches the doors close after Harry and Hermione enter next room.
Handheld:Ron gets injured from start, Harry have to answer three questions in order to make the pieces move and win.
Mountain Troll Chamber The Troll is already collapsed on the floor when Harry and Hermione arrive. Not seen. However a bit of the Chamber is shortly seen. Not seen. The Troll was collapsed but wakes up when Harry and Hermione get there. The Troll is still groggy so while Hermione tries to unlock the next door, Harry levitates the litter present in the room from out of the Troll's way, without making noise. The Troll doesn't notice a hole on the floor and falls into it. Not seen. GBC: Same as book.
GBA: Not seen.
Desktop: Not seen. However a bit of the Chamber is shortly seen.
Handheld: Not seen.
Potion Riddle Hermione solves the riddle; Harry goes through the Black Flames, Hermione goes through the Purple Flames to go get help as there is only enough potion for one of them to go through the black flames. Disc 1: Not seen.
Disc 2: The player must click on the right potion.
Harry solves the riddle by watching the 7 containers move, and must select the one that has the correct potion; Harry goes through the Black Flames, the Purple Flames disappear. Harry has to guess which knight has the Ice Potion. You must read the riddle and figure out the correct two potions. GBC: Harry has to mix and brew the potion, solving the riddle.
GBA: Harry and Hermione have to look for the four potion ingredients, scattered trough the dungeon.
Desktop: Not seen.
Handheld: Not seen.
Mirror of Erised Antechamber Not seen Not seen Harry has to push the blocks to get to the Mirror of Erised room, while Quirrell pushes the blocks back at him and tries to curse him. Quirrell brings suits of armour to life and summons one gigantic suit of armour. Not seen GBC: Harry duels with Quirrell.
GBA: Harry dodges Quirrell's curses, making him destroy the floor. Then, they both fall into the Mirror of Erised Chamber.
Not seen.
Mirror of Erised Chamber Harry struggles against Quirrell and Voldemort, but passes out before Quirrell dies. Harry struggles against Quirrell and Voldemort, watches Quirrell die, and passes out when Voldemort's soul passes through him. Harry tries to kill Quirrell/Voldemort by collapsing pillars on top of him and he also tries to deflect Voldemort's curses with the Mirror. Harry passes out at the same time Quirrell dies. Dumbledore then bursts in to the room. Harry tries to kill Quirrell/Voldemort by collapsing pillars on top of him and he also tries to boost his jinxes with the Mirror, and then directing it to Voldemort. Harry watches Quirrell die. You must find the Philosopher's Stone. (It was in Harry's pocket.) GBC: Harry duels with Voldemort and passes out when he touches him. He doesn't see Quirrell die.
GBA: Harry deflects Voldemort's curses with the Mirror and passes out when he touches him. He doesn't see Quirrell die.
Desktop: Harry battles with Quirrell, hurling his own green cursed heads back at him, after touching him 3 times Quirrell burns away and Harry passes out.
Handheld: Harry has to lit the torches to make the fire graves bubble with lava. Then some blocks appear, but when destroyed let go of a heavy object that knocks Quirrell out (Harry does this 3 times).


Notes and references

  1. Pottermore - book 1, chapter 16, moment 1

Hogwarts Castle
Locations below ground floor

Boathouse · Boathouse passageway · Chamber of Secrets · Conical Crypt · Dark Hall · Deathday Party Hall · Defence Against the Dark Arts dungeon · Detention escape route · Dungeons · Dungeon cave · Dungeon Corridor · Dungeon Five · Dungeon hall · Dungeon Pit · Dungeon Staircase · Entrance Dungeon · Forgotten Cavern · Hieroglyphic Hall · Hogwarts Basement · Hufflepuff Basement · Kitchens · Lever Rooms · Lost Tunnel · Lower Chambers Corridor North-East · Lower Chambers Corridor West · Lower Chambers Portrait Corridor · Poltergeist Passage · Porticus Circumscriptus · Porticus Periculum · Porticus Imago · Porticus Medius · Potion-Mixing Room · Potions basement · Potions Classroom · Prowling Passage · Quidditch cave · Room of Doom · Room of Runes · Severus Snape's office · Shop · Slug Pit · Slughorn's Stairs · Slytherin Boys' Dormitory · Slytherin Duelling Dungeon · Slytherin Dungeon · Slytherin Girls' Dormitory · Undercover route to the Kitchens · Underground Chambers · Vestibule of Mischief · 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

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