Long black curtains still bearing the stains and scars of a decade of potions accidents now hung across windows that had seen Harry's favourite lessons. Sullen silence lurked in the gloom.

He really isn’t helping himself with these vampire rumours.

Malfoy stared into the surface of his desk, ignoring a chattering Pansy. Hermione peered into the shadowed corners of the room and Ron buried his head back in their textbook.

'Something tells me this is no longer going to be my best subject,' Nev said.

'Herbology’s your best subject.' Harry scoured the shadows and caught a faint ripple in the air before the board. ‘I think the lesson’s about to start.’

He uses the Disillusionment Charm just for a dramatic entrance. Harry chuckled. Mine's better than his.

'Mr Weasley.' Snape appeared next to Ron's desk and snapped his book shut with a flick of his wand. 'While I am glad you have finally learnt to read, I have not yet told you to open your books. You need to listen before you learn.'

'Ah,' Nev whispered. 'Speech time.'

Harry grinned and caught Snape's eye when the professor narrowed his eyes toward their spot at the back of the classroom. I dare you, Snape.

Snape drew in a deep breath and prowled 'round the first row of desks. 'This subject has been under the care of no fewer than five teachers during your stint at this school. Each with their own methods, matters, and manner. With such… inconsistency, it is small wonder that so few of you have achieved the necessary level to study the Dark Arts for your NEWT.'

I'm fairly sure we took Defence Against the Dark Arts. Harry smirked to himself as Hermione writhed in her seat at the front of the class. Yeah, I bet you didn’t like hearing that.

'I will not lessen the infinite complexity of this subject with poorly referenced metaphor, or simile, nor—' his eyes dipped to Hermione '—will I ask that you commit entire tomes to memory. Neither is a viable approach to defend against something that evolves so swiftly, fluidly, and dangerously as the Dark Arts do.' Snape paused, moving back behind his own desk. 'If you want to survive them, you must become every bit as elegant, as subtle, as deadly, and as tenacious as they are.'

All this talk of dark. Harry smothered his distaste. It’s just emotion, intent, and power. Only people that don’t really understand glorify it like that. Adoration is the furthest state from understanding.

Snape whirled, summoning a handful of dead spiders, and sending them floating across the class until they each had a crumpled arachnid on their desk. Ron glared at his and poked it to the far side of his desk.

'When it comes to the Dark Arts, no number of books or words will truly help you understand what it is to face them.' Snape flicked his wand upward in a sharp, jerking motion, muttering beneath his breath, and the spiders spasmed back to life.

Hermione gasped. ‘Inferii!’

'Imagine that each of these spiders is a true, human inferius,' Snape drawled as the class dissolved into chaos. 'Deal with them as best you can, but try to avoid being bitten. They're mildly venomous.'

'Reducto,' Nev said, blasting his to pieces.

Well, that’s not going to work, Nev. Harry pinned his to the desk with the tip of his wand and tried to get a feel for the magic. Interesting, there’s no aggression or hostility. This isn’t the real deal, just a very similar enchantment. Snape knows what he’s doing.

Nev’s spider’s legs glowed with an eerie yellow aura and jerked back together. Pansy Parkinson shrieked as her spider put itself back together in her lap and scuttled under her shirt. Small flickers of flame began to bathe most of the desks, crisping and blackening the animated arachnids until they all fell still. Sore-looking red bites marked the hands and arms of most.

'Stop playing with it, Potter,' Snape drawled from the front. 'A true inferius will not stop just because you have touched it with your wand.'

Oh I beg to differ.

He imbued his adaptation of the withering curse into the spider and watched it crumble to dust.

'Were you facing an animated corpse, rather than a harmless arachnid—’ Snape gave the bite-covered Pansy Parkinson a withering look '—you would all, with a few exceptions like Mr Malfoy, likely be dead.'

The remains of the spiders vanished and Ron relaxed over the dark scorch mark on his desk.

'The larger the creature animated, the more magic is required,' Snape said. 'For something like a spider, there is little difference to us between an inferius and a living spider save their ability to put themselves back together. However, the gain in strength of an enchanted human corpse, or something of similar size, is much more effective, and remains within the realm of possibility. This is, aside from the psychological aspect, why most inferii are human.' Snape's eyes roved around the room. ‘Are there any questions?’

Hermione’s hand sprang into the air. ‘What’s within the realm of possibility, sir?’

‘There is no reliable account of anything larger than a horse or bull or shark being successfully turned into an inferius,’ Snape answered. ‘In the last war, the Dark Lord utilised inferii rarely, but Grindelwald used them extensively toward the end of his wars. There is a single account of him capturing and creating an inferius gryphon, but it was reputedly destroyed by Dumbledore’s phoenix within a few moments of its release.’

‘What about a dragon?’ Seamus called out.

Snape’s eyes flashed. ‘You do not shout out during my class, Mr Finnigan. If you do, an inferius dragon will be a blessing compared to the detentions I will give you.’ He tutted. ‘It is, however, an impossibility. Magical creatures of a certain class like dragons, unicorns, phoenixes and basilisks are all heavily influenced by the natural alchemical magic of their bodies. Even should a wizard possess the power to create an inferius of such a potent creature, which I can assure you is impossible, they would not retain the magical abilities that make them so fearsome. Your dragon would be unable to breathe fire, Mr Finnigan.’

A shame. Harry's momentary regret at destroying the corpse of the basilisk faded alongside the tantalising image of unleashing the seventy foot serpent inferius upon an unsuspecting Snape.

'Mr Malfoy, perhaps you'd be so kind as to explain your tactics in defeating your opponent?' Snape commanded.

Malfoy scowled. 'I used fire.’

'Three words is not an explanation,' Snape reprimanded. 'What Mr Malfoy means is that fire sufficiently destroys the physical body of the inferius to unravel the magic bound to it. There are other ways, but fire is amongst the most efficient.'

'Can we not just blast it to pieces?' Someone called out.

'I suspect, Mr Smith, that any attempt made to cast that many powerful blasting curses before the inferius reaches you would fail spectacularly. The corpse would tear you limb from limb, before its master added the remains of your foolish self to his collection of inferii. Are there any other foolish questions?'

Hermione’s hand crept into the air.

‘Miss Granger…’ Snape’s lip curled. ‘I ought not be surprised, I suppose.’

She chewed her lip. ‘Did you add to the spell? Our spiders weren’t very aggressive…’

Snape nodded. ‘That is a smarter question. I stripped out that part of the enchantment, because while we are headed for troubling times, we’re not yet so desperate to unleash true inferii in the classroom. A wizard or witch that knows the magic well may be able to alter the enchantment, although this usually isn’t to make them safe for study.’ His eyes darkened. ‘The Dark Lord often imbues his with a strong resistance to fire, which can make them an effective weapon against most wizards and witches, especially if they’re unable to escape.’

Ron’s hand inched up. ‘Are we going to see them being used by Voldemort?’

‘The Dark Lord has used them in the past, so I wouldn’t rule it out. However, multiple inferii are hard to keep tight control over and easily evaded by anyone capable of apparition.’ Snape’s wand flicked and their books all snapped open. ‘I expect, on my desk at the start of our second lesson next week, fourteen inches on the characteristics of inferi and how to counter them. After that point, we will move on to cover other dangerous creatures you are likely to encounter, recapping werewolves, giants, and covering lethifolds in more detail. You may use the remainder of this lesson to begin planning and researching, either here or elsewhere.'

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Dumbledore chose this curriculum carefully. All of Voldemort’s likely allies are on it.

'For those of you who were... unable to handle your spider—' Snape's upper lip curled '—Madam Pomfrey will be able to get rid of the rashes in a few seconds. I suggest a brief trip to the hospital wing, else you will spend the rest of the day in discomfort.'

Pansy swept all her stuff off the desk and stalked out.

'Why are the rest of you all still here?' Snape drawled.

'Good question,' Neville muttered, packing up his stuff. 'I have a free period next, so I'll be in the common room planning this and listening to Parvati and Lavender gossip about Hermione's nightmares. I'll see you after you've endured Advanced Arithmancy.'

Nightmares? Harry watched Hermione disappear out the door. Is she using a time-turner too much like I was?

'I don't remember asking to speak with you, Potter,' Snape said.

'Professor Dumbledore has offered me the opportunity to take my NEWTs early, should I have written permission from the subject's professor,' Harry said.

And you better give it, especially after handing Katie’s address to Voldemort.

'And you expect me to grant this permission?' Snape's sneer crept back.

'I can demonstrate if you like.' Harry let a little ice creep into his eyes. ‘I’ve been practising since Katie nearly got killed in Diagon Alley. Just in case I find the ones responsible.’

Snape’s brow creased. 'I will indulge your suggestion. I will cast a jinx at you and you will block it. Silently.' His wand flashed up, casting three sizzling orange curses.

Harry threw up a blinding wall of silver light without a word.

'That's enough, Harry,' Snape gritted. 'I do not want to have to have Madam Pomfrey fix my eyesight because of a simple shield charm.'

He let it drop.

'It seems that I was mistaken to warn you last year that the Dark Lord had taken your boasting seriously,' Snape murmured. 'Perhaps I would have done better to warn the Headmaster that you were taking things seriously. You cast that just by touching your wand.'

'Did you warn him?' Harry asked.

'No,' Snape replied. 'You will find, Harry, that unless you yourself are the utmost extreme of opinion, you must make do with living in between others' ideas. Dumbledore would be devastated to learn that you’ve marred your soul by casting the Killing Curse. He suspects you are not so innocent as you appear, but still clings to the hope that you’re not irredeemable.'

'Nobody, no matter the nature of their crimes, seems irredeemable in his eyes,' Harry whispered. ‘A single, selfish spell seems far less a crime than others I’ve learnt about.’

'So you know,' Snape said. 'He told you, I presume.'

'Dumbledore did.’

'I will not ask for your forgiveness, Harry, nor do I expect you to forget what I have done.' Snape's stoic countenance crumbled into something hollow. 'You're the only person who lost more than I did that night.'

You lost nothing you didn’t deserve to lose.

He kept his expression blank. 'My NEWT exam, sir?'

'You have my permission,' Snape said. 'I will write a brief note to the headmaster. Do you intend to attempt your other subjects early as well?'

'I do.’

'Good.’ The corner of his mouth crooked into a hint of a smile. 'Your mother was a dedicated, brilliant witch; one who would have been ashamed of the talent you have until recently been squandering.'

If you thought so highly of her, you shouldn’t have got her killed. Harry crushed the fist of ice clenched about his heart.

'Professor McGonagall will not think twice about allowing you,' Snape continued. 'And neither will Professor Flitwick, but I don't think you will convince Professor Vector, and nor will you manage to sway Professor Slughorn as you are.'

'I'm a competent brewer,' Harry said.

'Competent, certainly,' Snape said. 'But Professor Slughorn will only let you risk escaping his influence early if you are truly exceptional or already indebted to him. He is a consummate Slytherin—' the smirk returned to Snape's lips '—much like yourself, though in a different vein.'

'I want four subjects,' Harry said.

‘You should want four. Which means we will have to make you appear as a prodigious potioneer, one at a level few others have reached at your age.'

'More extra lessons,' Harry deduced.

'A few tips here and there.’ Snape’s dark eyes softened a fraction. ‘Teaching is not about forcing children to recite recipes, it’s about getting them to learn how to learn. You, like several others, consistently get an E, because you can perfectly reproduce the work of another, but you do not demonstrate anything creative or original yourself.’

Harry pursed his lips. In theory, it’s not so different from the rituals I’ve been doing. In practice, there’s probably a lot of middle ground between the web of intent I know how to create for a ritual and making a potion out of it.

'I would be a fool to pass up tips,' Harry said.

'Yes, you would.' Snape summoned a glass goblet from within his office and poured himself a drink of a very dark red liquid. 'Blackberry wine.' He took a sip. 'I enjoy a glass from time to time during the day. It eases the frustration of marking and teaching, amongst other things. It is also, no doubt, the source of those ridiculous rumours about my vampirism.'

Other things being spying for both Dumbledore and Voldemort, the guilt from betraying your only friend to her death, and any shred of regret he has for almost sacrificing students. Harry noted the neat row of glass goblets sparkling on the shelf within Snape’s office and a bubbling cauldron spewing thick, white mist across the surfaces and onto the floor.

'For now, the basic principles of true brewing will serve you best. It requires innate talent to truly grasp any branch of magic, though—’ Snape’s eyes flicked to Harry’s ‘—the magic you cast upon your eyes suggests you already have a grasp of this that exceeds most.’

‘I’ve picked up a few things.’ Harry allowed himself a small smile. ‘All sorts of interesting, abstract bits of magic, really.’

‘I see. Well in potions that will serve you well. However, to apply it, you still need to understand exactly how each ingredient and how it’s prepared will affect your potion.’ Snape finished his goblet of wine, setting the glass cup down on his desk. 'This is something it takes years of experience to acquire. If you impress Slughorn enough, he will go out of his way to favour you, and in so doing, later favour himself.'

‘I’ll have to impress him then.’

'You are running late, Harry,' Snape said. 'Professor Vector is unlikely to let you take her subject early anyway, but you're not helping your case.'

Harry swept out. For now, he’s useful. I need that fourth NEWT, or I’ll be stuck even if I’m victorious. A small smile crept across his lips. And I suspect he’s fully aware of that. He knows he has to dance between Dumbledore, Voldemort and myself, now.

'Just on time, Harry,' Professor Vector announced as he slipped in. 'I was just starting to go over our material for the year.'

'Sorry, Professor Vector,' Harry said. 'I needed to speak with Professor Snape about my NEWTs.'

'Ah.' Professor Vector nodded. 'I've heard rumours of this. I'm afraid, Harry, that this winter is altogether too early for you to be taking a subject this complex. However, should you prove yourself capable, I might be open to letting you take it this summer instead.'

Disappointing, but not unexpected. Harry took the remaining free seat beside Hermione. Defence, Transfiguration, Charms, and Potions it will have to be, then.

'Thank you, professor,' he said.

At the front of the class Professor Vector sketched four dimensional matrices in bright, green fire. ‘Every spell, enchantment, or piece of magic can be described as a magical mapping of one thing to another. Of course, the more complex ones require incredibly complicated mathematical models to describe the mapping, and in most cases we simply don’t have an understanding of magic detailed enough to be capable of that. For simpler pieces of magic like apparition, we can write out a transformation matrix that allows us to mathematically model exactly how magic folds our dimensions to allow us to apparate.’

Harry groaned. I prefer purple runes. And I hate matrices.

Hermione scribbled her way through a page of notes in increasingly obscure shorthand notation.

I miss the simple stuff I didn’t have to pay attention to already. He sighed and began to write. Fleur's always going to be better than I am, anyway. A gentle ache tugged at his heart as he worked his way through the lemmas and the reflection of the green-eyed, silver-haired girl in the Mirror of Erised welled up amidst the matrices. I can’t wait to be done with all this.

‘Did you really think you’d be able to take this exam in four months' time?’ Hermione hissed. ‘That’s deluded, Harry.’

‘Rude.’ He shot her a sharp look. ‘But no, I’ll need all two years for this one. The other four I should have a good chance with.’

She chewed her lip. ‘You are the best in the year at Defence and Transfiguration, and I doubt you’ll struggle with Charms, but potions… You only got an E.’

‘I’d be happy with another E,’ Harry replied. ‘But yes, potions is the one that will be tough. Fortunately, I can skive off all my other lessons and just focus on that.’

Hermione huffed. ‘You know that school isn’t just about exams, Harry. It’s important you socialise with your peers while your brain is developing, it affects how the brain develops.’

‘Says the girl who spent a month in the library not talking to anyone and not sleeping before our OWLs,’ he retorted. ‘I’ve got more important things to do than listen to the girls gossip about you having nightmares.’

Her expression darkened. ‘I don’t have nightmares.’

Harry snorted. ‘Sure.’ He took a deep breath. ‘Listen, Hermione. I don’t particularly care whether you think I’m doing the right thing or not, but you can keep your thoughts to yourself. I’ll do the same, since that’s only fair. You can do you. I will do me. Does that sound bearable to you?’

Hermione’s fingers tightened around her quill. ‘You’re not the same boy I was best friends with.’

‘And whose fault is that, Hermione?’ He shuffled his chair away from her and bent over his notes, ignoring her muttered response.

Not completely yours, of course. But you were there, watching me try to play hero until I slipped back into the emptiness and drowned. He stifled a shudder and tried to smother the ache beneath his ribs. Fleur’s face hovered behind his closed eyelids, a soft warm smile on her lips. Fleur and Salazar dragged me out and I’m not going back. Not ever.