She has been teaching for thirteen years when Severus Snape first sits in her classroom. He is black-haired and black-eyed, like his mother, and largely unassuming. At eleven, his eyes burned with hopes not yet broken, and Minerva gets the niggling feeling that this child, coming to her in an auspicious year and with a ready mind, will be her undoing.
Over the next seven years, she watches him rise above all expectations, surpassing Slughorn's skill in Potions by sixteen. He's shy, the ghost of the dungeons and the library, but his eyes still burn with knowledge not yet gained. She thinks he's like her, trying to force the rest of the wizarding world to see a lowly half-blood as one of the brightest minds of their age. Somehow, that's reassuring, even as his quest for recognition takes him on ever-darker paths.
She watches him fall, making one regrettable choice after another until there is no path out. She watches him become a Death Eater, willing to lie through his teeth about his father for acceptance; when she happens across Tobias Snape's obituary, she only surprised by the lack of gore. She watches him sell out what few beliefs he had ever kept. She watches him sell out Lily.
Later, after the war ends, she considers asking him if the benefits of that decision were worth the cost. She never does; he is too busy being wrapped up in self-loathing and grief to answer her even if she had. They don't talk much in peacetime, and when they do it's bitingly cold and filled with anger. His eyes don't hold fire anymore, only darkness and anger and (maybe) regret.
Then Harry comes. Harry, who looks more like a young Severus than a young James if she's being honest with herself. Harry, who talks so little she'd never notice him if he was anyone else. Harry, who Severus hates with the intensity of a thousand suns simply for being born. Needless to say, there are many, many not-yelling matches between them those first few months; they have never yelled at each other when they were truly angry, and Minerva is furious.
It all comes to a head that Halloween night, when Harry and Ron decide that saving Hermione is more important than saving themselves. She is torn between thanking God that they're all alive, congratulating them on their accomplishment, and yanking her hair out by the roots. It's admirable, of course, that her lions are so brave at eleven, but Minerva has always believed that true bravery needs to have some planning and brains behind it and this had none.
She finds Severus in her office after the children have been seen to bed, drinking her firewhiskey and borderline hysterical about the whole affair. "He's Lily's son!" he shouts, laughing at the implications. "Did you see the troll? Evans' courage and James' stupidity. He's Lily's son."
"I know," she says quietly, and this next part might hurt his feelings but she's never been anything if not direct. "He is Lily's son, Severus, and has been this whole time." Snape doesn't answer, but she hadn't expected him to in the first place. Still, Harry doesn't complain about his unfairness as often, which either means he's gotten his head out of his ass or Harry doesn't trust her anymore. When Christmas rolls around, there's a large bottle of the best alcohol money can buy on her desk; she puts it in a cabinet for special occasions.
That bottle becomes their little secret, to be broken out at the end-of-year crazy adventure. Snape always leaves her office drunk and grumbling about Evans recklessness defying all common sense on those occasions. As much as she dislikes him, Minerva has to agree with that point; somehow, Harry manages to get into (but not necessarily out of) more trouble than the Weasley Twins ever do, and that fact is frankly terrifying.
There's the end of his first year (Minerva's thirty-third, Severus' eleventh) when he decides to protect the stone by breaking through a gauntlet of traps. More specifically, he gets through their gauntlet, which is both humbling when they first learn of it and unnerving when they realize something seriously undermined their protection. That night involves a lot of drinking, and they both spend a disproportionate amount of time lurking outside the Hospital Wind until Harry wakes up.
Everything escalates in the utter clusterfuck of his second year, which starts with a petrified cat and ends with him fighting a basilisk. Of course, everything seems normal at first, with the possible exception of Lockhart quickly earning the dishonorable title of Most Hated Teacher of the Century among the staff. Again, it is on Halloween that everything goes to hell; Mrs. Norris is found hanging from a torch bracket and the first people on the scene are her Golden Trio of idiots.
One night in that cursed year, Snape confesses to her (privately, and while most likely drunk, of course) that Lily could also speak to reptiles. No, not just snakes, but all manner of scaly and cold-blooded creatures. Apparently, it was one of the more important reasons Petunia hates magic. When she presses for more details, Snape gives her a story of the three of them at thirteen, when their tempers ran hot in an even hotter summer. Petunia had decided, for whatever reason, to turn Cokeworth against the recluse of Spinner's End and her sister; at the time, it had felt like the whole world. Lily, feeling vindictive, and Severus, being Severus , had sought revenge; there had simply been a lot of snakes, lizards, and turtles around that summer. He outlines what sounds like a terrible prank (but oh, that was Lily all right - it took a lot to push her over the edge, but hell had no fury like her when she was well and truly angry) in nostalgia and childish hopes; their third year, Minerva remembers, was near the end of a peaceful lull so long some had thought the war was well and truly over.
At the end of the year, with Ginny (little Ginny, the only girl in a family of brothers, who had stood on that platform since she was barely old enough to toddle) missing and Harry and Ron looking for her, Minerva seriously considers retirement. These kids are going to give her a heart attack one day, and probably sooner rather than later. When they all turn up more or less unharmed and with an obliviated Lockhart in tow, she sighs in relief and tells her heart that it can stop beating quite so fast. It stubbornly refuses; with these three, the fight is never over.
Their third year is, somehow, the calmest, despite there being a mass murder on the loose and a werewolf in the castle. She knows Sirius Black, taught him magic and disciplined him for seven long years; she knows that he hates to leave jobs unfinished and crimes against him (and, at one point, Peter, James, and Remus) unavenged. She knows he read all the books in the Hogwarts Library on Animagi cover to cover, and suspects that he is one now. She knows he is coming, presumably to kill Harry.
She wants to see him try. Harry now lives in one of the most heavily warded structures in Britain, with friends at his back and by his side. Hogwarts is now ringed with dementors, and the two people who knew Sirius best are just waiting for him to come.
Third year goes just like the others: looming danger, sudden threat, active danger, Harry saves the day, no one outside of Hogwarts is notified. Scabbers is gone, but Minerva had honestly never liked that rat anyways. Harry is alive and unharmed; that's all she was hoping for.
Minerva tries to hide her sigh of relief at the tournament's announcement. Harry is far too young to enter, so she should just have to worry about her of-age students. There is no stone, no diary, no looming danger just outside the castle walls. That relief sharply ends, yet again, on Halloween, when Harry's name comes out of the goblet. The rest of that year is worrying. After Harry lands back in the stadium, clutching Cedric's dead body and declaring Voldemort is back, Minerva doubts that she will ever sleep again.
His fifth year is terrifying, and not just because Voldemort is back and the Ministry won't listen. Snape has seemingly forgotten the lesson he learned so well five years ago, so she alone has to act as a buffer between Harry and everyone out to destroy him. Umbridge is not smart and not careful, but that's what makes her so dangerous; she doesn't see the risks she's taking and lines she's crossing as boundaries at all, at least not how anyone with ethics or common sense or the slightest understanding of muggle history would perceive them. She starts keeping murtlap essence in her office and carefully turning a deaf ear to all talk of this (illegal) "DA" club.
It all falls apart for Umbridge in the end, and Minerva has never been prouder of the Weasley twins than when they left. Just watching the pink menace disgraced almost makes her smile. The Ministry finally gets a clue and the war starts in earnest.
The war years are some of the longest of her life. It's not her first war (she had grown up during World War II and taught while Voldemort gained power, after all), but something about this feels different. There is nowhere to hide this time, no codes to crack and no prophesized savior; they can only wait and hope for Voldemort's death.
Snape goes manic, trying to keep up two fronts in what could be another decades-long conflict. Dumbledore is dying, and he is having difficulties telling anyone what to do after the fact. Harry is struggling with the destiny he never wanted, and it is her job to protect him, even after he never comes for his seventh year. It is her job to protect all of them, even the students who are not hers. The job grows unbelievably hard, trying to protect everyone single-handedly; Snape does his best, but he is playing two sides and failing dismally. There are precious few hopes left when Harry returns with a (bad) plan and (weary) friends. Less than an hour after they set foot in the castle, the battle is on.
The Death Eaters have surrounded the castle. Many of them were her students; she knows them, even if they have gone down dark paths since then. There are ones she can recognize even in uniform, and still others she knows are there. They are not exactly intelligent, any of them, but they are willing to use the Unforgivables against children and uncaring of the consequences. Silently, Minerva promises herself that they won't get the chance, not tonight, not while her heart still beats.
The Battle ends as abruptly as it began, with Voldemort gone forever (they think) and over a hundred injured, dozens dead. Among the corpses are Death Eaters who fought long after they had a hope of winning. Among the corpses are some of her favorite students, willing to die for what they believed in. Among the corpses are countless adults who she can see clearly as bright-eyed children, eleven and in awe of magic. Among the corpses is Snape, his eyes closed forever.
The funeral is a quiet affair; he did not leave any family behind, any lovers, any friends. He looks peaceful in death a way he never could in life, a bouquet of lilies in hand. She never visits his grave afterwards, unwilling to waste time on the past when so many small hands are dragging her towards the future. Still, there will always be a space in her heart that twinges whenever a child, looking for help in History of Magic, asks her about Severus the Brave that just doesn't when the figure is Hermione the Wise or Ron the Loyal or anyone still alive. She keeps that space for the dead people that changed her just as much as she changed them; she keeps it for the boy with fire in his eyes who changed the world in ways he never intended.