There are spoilers within for those who haven't read to the end of the Harry Potter series - be warned!
'"Better Hufflepuff than Slytherin,' said Hagrid darkly. "There's not a single witch or wizard who went bad who wasn't in Slytherin."' (Harry Potter and the Philosopher's Stone)
That, right there, is our introduction to Slytherin: the most infamous of the four Hogwarts houses. More importantly, it's also the first thing Harry Potter hears about Slytherin… the house which at some point has nurtured every one of the enemies he will encounter as he grows up, from Draco Malfoy to Voldemort himself.
Who can blame Harry when he begs the Sorting Hat not to put him into Slytherin - despite the Hat's suggestion that he would do well there?
It's not hard to see that Slytherin is meant to be the Big Bad of the Hogwarts houses. By giving Slytherin a snake as its emblem, Rowling taps straight into a long vein of serpent mythology from the Bible to Disney's Aladdin; from Medusa and the Gorgons of Greek Mythology to Conan Doyle's The Speckled Band, the snake has long been a symbol of… well, let's just say it's not good.
Slytherin doesn't exactly attract a friendly crowd, either. Again, Harry's early impressions (and ours as readers) formed by watching them at the Sorting ceremony are that they "looked like an unpleasant lot." They embody a creeping cold; a chill you can't quite shake - it's no coincidence that the teacher most associated with Slytherin (of whom more later) is described as having eyes which were "cold and empty and made you think of dark tunnels." Their common room is a dungeon, and worst of all… they cheat at Quidditch.
They're a bad bunch, made up in our experience of bullies (Millicent Bulstrode), mean girls (Pansy Parkinson) and thugs (Crabbe & Goyle). There's more than a hint of an unsavoury belief system there too: of corruption and prejudice and sheer malice in Slytherin's collective obsession with "pure" blood.
And then there's Draco. A snob, indulged since birth and convinced of his own superiority, Draco is Harry's nemesis at Hogwarts… or is he? Draco may cast himself in that role, but we know better. Harry's true nemesis is a much more frightening figure. As the series progresses, Draco manages to become less threatening, not more. His induction into the Death Eaters and subsequent mission to kill Dumbledore marks him not as a fully-fledged Dark wizard… but as an inexperienced child who has bitten off more than he can chew - something we see Dumbledore comment on to Snape in The Deathly Hallows: "A frightened teenage boy is a danger to others as well as to himself. Offer him help and guidance."
…Which brings us back to Snape himself. The Slytherin house-master, he seems to embody its essence perfectly with his greasy hair, sallow skin and hooked nose - not to mention his hatred of Harry. We aren't surprised to learn that he was once a Death Eater - nor are we shocked by his apparent treachery. That's what Slytherin stands for, after all. Time and time again we are warned not to trust members of this particular house, from the Sorting Hat's song: "Those cunning folk use any means / To achieve their ends", to the portrait of Phineas Nigellus Black, who tells Harry: "when given the choice, we will always choose to save our own necks." So why should Snape's behaviour be any different?
The answer, we learn is simple. Told in flashback through Snape's memories in the closing chapters of the saga, we finally understand that there's a greater power at work in his actions. Love.
"'But this is touching, Severus," said Dumbledore seriously. 'Have you grown to care for the boy, after all?'
'For him?' shouted Snape. 'Expecto Patronum!'
From the tip of his wand burst the silver doe; she landed on the office floor, bounded once across the office and soared out of the window. Dumbledore watched her fly away, and as her silvery glow faded he turned back to Snape, and his eyes were full of tears.
'After all this time?'
'Always,' said Snape."
Just like that, along with Harry, we learn that throughout Snape's life, he has loved Harry's mother, Lily. It this love which redeems him, just as it was Lily's love which saved Harry. Love is the driving force for good in the Harry Potter universe - and for all his faults, even Severus Snape is not immune.
That's the real secret of Slytherin. That all of the scheming, all of the corruption and cynicism and downright evil can be undone. Not easily - it takes huge sacrifice and courage, but the darkness can be overcome. Slytherin's role is to represent not just the greater evils in the world but the lesser ones: every bully we faced at school, every teacher who humiliated us, every tell-tale and tittle-tattle, every petty-minded boss. Slytherin exists to show us that even in the darkest, dankest places we can find hope - hope in Snape's final moments, hope in Dumbledore's determination to save Draco: "'That boy's soul is not yet so damaged,' said Dumbledore, smiling. 'I would not have it ripped apart on my account.'"
Perhaps, if Slytherin had been a different house -more like Hufflepuff or Ravenclaw, the story would have been very different. What if Slytherin was more like Gryffindor? What if they had turned on Umbridge during her tenure at the school? What if, shamed that one of their number suggested handing Harry over to Voldemort, the Slytherins had refused to abandon Hogwarts before the final battle - as so many of the other students did? What if, instead of following Voldemort, they had turned against him? Perhaps if things had gone differently, such great sacrifices would not have been necessary - but conversely, we would not be left with the sense of victory, the sense of hope that the series ends with… hope tinged with loss, undoubtedly, but hope nonetheless.
Thanks so much, Lou! Brilliant article :-)