It’s not really surprising that Hogwarts’ Chamber of Secrets is the subject of speculation. A secret underground chamber that can only be accessed by the heirs of Salazar Slytherin – a wizard with a preference for pure-bloods and a rumoured fondness for the Dark Arts – is not exactly something you’d put on the school prospectus.

But it is a great exercise in sorting wizarding world fact from fiction…

Myth 1: the Chamber of Secrets doesn’t really exist

The biggest myth surrounding the Chamber of Secrets is that it doesn’t exist at all. Professor Binns is adamant that the idea of Slytherin first creating a chamber unknown to the other Hogwarts founders, and then magically sealing it with some sort of horrifying creature inside, is ludicrous. He points to the fact that many learned witches and wizards have searched over the years and none has been successful.

But, as Parvati Patil says, that could be because Slytherin used Dark Magic to seal it. Which, of course, he did, meaning that only wizards with Slytherin’s ability to speak to snakes are able to open the Chamber.

Myth 2: only Dark witches and wizards can talk to snakes

Salazar Slytherin and many others seem to think only witches and wizards with a shared affinity for Dark Magic can speak Parseltongue, the language of snakes. Which, as Harry proves, is another myth.

It’s something that worries Harry though – when he finds out he shares his Parselmouth status with Voldemort, he remembers the Sorting Hat’s suggestion that he might do well in Slytherin. But he chose not to join that house precisely because he wanted nothing to do with the Dark Arts. As Dumbledore says, it’s this choice that defines Harry, and even the most skilled practitioners of Parseltongue have choices.

Myth 3: only the heir of Slytherin can open the Chamber of Secrets

If most people think only Dark wizards speak Parseltongue, and the Chamber of Secrets was sealed by history’s best-known Parselmouth, you can see how the idea that only Slytherin’s heir could access the Chamber solidified into myth.

It’s not strictly true, though, because anyone who can speak Parseltongue can open the Chamber and, despite Voldemort-as-Tom-Riddle’s assumption, not all are Slytherin’s descendants. Ginny Weasley opens the Chamber under the influence of Tom Riddle, and Harry – who only ever uses Parseltongue to save someone – opens it to rescue Ginny. Neither of them is Slytherin’s heir. Although, as Dumbledore says, Harry’s ability to speak Parseltongue is a skill accidentally transferred by Slytherin’s actual heir, Voldemort, when he tried to kill Harry as a baby. So perhaps this is one myth with a bit of truth to it.

Myth 4: Hagrid opened the Chamber 50 years ago

If people really believe that only Slytherin’s heir can open the Chamber of Secrets, it’s hard to credit that Tom Riddle’s framing of Hagrid was ever taken seriously. But it was, as Riddle reveals to Harry through the medium of his diary.

When Moaning Myrtle was killed by the creature lurking in the Chamber of Secrets, Hagrid’s love of frightening beasts left him open to suspicion. Riddle used this, revealing Hagrid’s care of one such creature, Aragog, and implying that Aragog was the beast wreaking havoc on Hogwarts. Given that Aragog answered only to Hagrid he was an easy scapegoat, but Hagrid’s expulsion from Hogwarts was as unjust as Riddle’s reward.

Myth 5: Slytherin’s monster was a gigantic spider

Aragog is a huge, hairy, very frightening-looking spider with lots of eyes and razor-sharp pincers. He’s a scary beast all right, and his appearance at the time that the Chamber of Secrets was first opened, combined with his natural inclination towards eating people, did give Hogwarts staff pause. But Aragog is not Slytherin’s monster.

Slytherin’s monster is a Basilisk – a giant serpent that can kill people with one look. Aragog and his colony of spiders are terrified of it. When Hermione discovers the Basilisk is getting round Hogwarts through the pipes, it all fits together. The reason Slytherin could control it, and the reason Riddle and Harry can hear and speak to it, is because they all speak Parseltongue.

Myth 6: the Malfoys are heirs of Slytherin

If Hagrid makes an unlikely Slytherin heir, then there is a more obvious candidate. Draco Malfoy is vicious in his treatment of those with Muggle heritage, and his equally morally repugnant father Lucius is a known Dark wizard with a number of Voldemort’s old school things. You can see why Ron and Harry suspect Malfoy might be the one attacking Muggle-born students.

So it’s a surprise to find out Malfoy’s as confused as everyone else. The only thing he is heir to is his family name, and as his father doesn’t see fit to tell him about plans their house-elf Dobby is aware of, it seems he has a way to go yet…