Once there was a wizard called Severus Snape. He was tall and lanky, and his black greasy hair hung like curtains around his face. He grew up as a half-blood wizard in an unhappy family, but found solace in a witch called Lily Evans, a childhood friend. Snape loved Lily deeply: through their years at Hogwarts; through her marriage to another wizard, James Potter; through his time as a Death Eater; and long after her murder at the wand of Lord Voldemort. After her death, a heartbroken Snape took up a position at Hogwarts as Potions Master (under Dumbledore's protection), and began his secret mission to keep safe the only thing that he had left of her: her son, a boy with his mother's eyes.
Severus Snape and the Philosopher's Stone
Still, that didn't mean that he had to like the guy, who looked annoyingly like his father (and Snape’s school bully) James Potter.
Nonetheless, Snape had a job to do. During Harry’s first year, Dumbledore and Snape suspected a fellow teacher, Defence Against the Dark Arts' Professor Quirrell, of trying to steal a precious magical object hidden within Hogwarts grounds: The Philosopher’s Stone. Because he's clever, Snape saw through Quirrell's plans pretty quickly, which involved setting trolls loose in the dungeon, and trying to jinx Harry Potter’s broom during a Quidditch match. Snape, of course, gallantly confronted Quirrell, but in the end, Harry and his two friends got all the credit, with Snape getting set on fire in the process. Charming.
Severus Snape and the Chamber of Secrets
Although this was a quiet year for Snape, his excellent teaching subtly led Hermione and Harry to discover two things that would prove paramount in their later years: Polyjuice Potion, and Expelliarmus. Unlike some wizards, he didn’t spend every year of Hogwarts trying to make himself the centre of attention.
Severus Snape and the Prisoner of Azkaban
This is the story where our hero had to confront the villains of his past: Sirius Black, Remus Lupin, Peter Pettigrew and James Potter – the bullies of Snape's youth, with one of them happening to be the man who married the love of his life Lily.
The unwelcome reunion occured when Potter’s old friend Remus Lupin secured Snape’s dream job of Defence Against the Dark Arts teacher. As Potions master, Snape kindly helped out Lupin – a werewolf. Of course, when he had to take over Lupin’s lesson, he may have accidentally taught his class how to spot a werewolf, but that was a complete coincidence.
Meanwhile, Sirius Black had escaped from Azkaban and is after Harry Potter. Not forgetting their years at Hogwarts, Snape wasted no time in trying to bring Black to justice when he came to the school. Towards the end of the year, Snape finally caught him in the Shrieking Shack. Once there Snape was hailed as a hero by Minister of Magic, Cornelius Fudge, who promised that he would be duly rewarded. The Order of Merlin! A profile in the Daily Prophet! Finally, everything's coming up Severus!
Some other stuff happened after that but it wasn’t really that interesting.
Severus Snape and the Goblet of Fire
As Hogwarts celebrated the return of the Triwizard Tournament, Snape had bigger fish to fry.
For his days of being a Death Eater were coming back to haunt him, and his Dark Mark – a magical stamp tied to the Dark Lord – was becoming more and more pronounced. His worst fears were confirmed later in the year when it was revealed that the Triwizard Tournament had inadvertently helped provide a cover the return of his old master, Lord Voldemort.
Cometh the hour, cometh the Severus. Upon Dumbledore's request, Snape ended the story by embarking on a dangerous, top-secret mission: to once again join the Death Eaters, and become a double agent.
Severus Snape and the Order of the Phoenix
Dumbledore assigned Snape yet another task, and it may have been Snape’s biggest mission yet: to hang out with Harry Potter. Alright, it was actually to teach Harry Potter Occlumency, the delicate art of defending your mind against intrusion – specifically, Lord Voldemort's intrusion. It's difficult magic to master, and requires an immense amount of mental control. He may as well have been teaching a flobberworm to tap dance.
Far worse than being useless, however, is being a weird, impertinent sneak – the kind who sticks his head into your Pensieve when you're out of the room. Who does that?!
Nonetheless, he aided Harry multiple times throughout the year: giving Dolores Umbridge fake Veritaserum; lying that he had run out of it when pressed for more; passing on Harry's message about Sirus's capture to the Order of the Phoenix; and therefore deducing that he had walked into a trap at the Ministry. Despite all his efforts, everyone still thought he was the worst.
Severus Snape and the Half-Blood Prince
Albus Dumbledore was dying, having just got back from a mission to destroy one of Lord Voldemort's Horcruxes, a ring, which cursed him, and handed him his death sentence.
Shocked and saddened, Snape reluctantly agreed to help Dumbledore with one of his final plans, and even helps lengthen Albus’ short life. While juggling Dumbledore, Lord Voldemort had assigned one of Snape’s students, Draco Malfoy, to assassinate Dumbledore; Dumbledore ordered Snape to do the deed instead, and to look after Hogwarts after he's gone.
Meanwhile, Potter was nosying around in Snape’s affairs once again – having found an old Potions book Snape used to write in and create spells under his nickname ‘The Half-Blood Prince’. But Snape didn’t have time to get too deeply into that.
Later in the year, Dumbledore revealed that Harry was in fact a Horcrux, meaning that he would eventually have to die. Now, as firmly established, Snape was not the greatest fan of Harry, but that doesn't mean that he ever stopped loving Lily. Dumbledore was surprised that Snape seemed to care for the boy. With a swish of his wand, Snape conjures up a Patronus – Lily's Patronus, a doe. 'Always,' says Snape.
In the end, Snape performed his duty, killing his closest ally, his dearest friend, and branding himself as a murderer in the eyes of the people he sought to protect. For that was the sort of man Severus Snape was: a hero so heroic that he would cast himself as the villain – as long as it meant doing the right thing.
Severus Snape and the Deathly Hallows
Locked in Voldemort’s circle, Snape set to work following Dumbledore’s final wishes, all the while appearing loyal to the Dark Lord.
He was made Headmaster of Hogwarts, where he secretly upheld his vow to Dumbledore to protects its students – especially as a pair of rancid Death Eater siblings, the Carrows, had been made Deputy Headmasters. Yet despite the danger of his mission, and despite being hated by most of the wizarding world, Snape held on to the one thing that kept him going: the safety of Lily’s son. He even sent his Patronus to guide Harry Potter to the Sword of Gryffindor (a known Horcrux-killer) in a nearby lake.
Months later, Potter returned to Hogwarts for one final battle – between good and evil, between the students and teachers of Hogwarts and the dark forces of Lord Voldemort. Still committed to his mission, Snape was cast out of Hogwarts by the other teachers, who were completely unaware of Snape’s good intentions.
Snape returned to the Dark Lord – but something was wrong. Voldemort was acting strangely, confused about why his Elder Wand would not obey him. Snape tried to reassure him that he was wrong, but Voldemort believed Snape to be the real master of Dumbledore's former wand, as he was the man who killed him. Snape realised what this meant but wasn't quick enough – Voldemort's snake Nagini was already on him, biting down into his neck, leaving him fatally wounded.
Yet in his dying moments, Snape performed one last heroic act. He completed his mission, his vow to Dumbledore, by giving Harry (who, unknown to Snape, was hidden nearby) the memories that would not only allow the boy to defeat Voldemort, but redeem him in the eyes of a boy he only ever wanted to protect – in Lily’s eyes, who looked into his for one last time.
And with that, Severus Snape slipped away.
Severus Snape died a hero, but died knowing barely anyone knew it. Nineteen years later, however, an older, wiser Harry would explain to his young son Albus Severus Potter why he named him after two great Hogwarts Headmasters, telling him that Severus Snape was 'the bravest man I ever knew.’ His legacy in Lily Potter’s family lived on forever.