A/N: Originally written in March 2010 as a birthday gift for mimimanderly on LiveJournal. This is still not really finished in that there is a missing scene I think it would benefit from, but I think at this point that I am probably not ever going to write it, so I've just papered over the join in the hope that it won't be too bumpy of a ride. Betaed by coyotegoth and by inamac, who is largely responsible for Lucius's letter as it appears here.

Warnings/Contains: Abuse of frogs (animal testing, not sadism), blood, self-inflicted wound (not self-harm in the usual sense), masturbation.

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For Enemies

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June 14, 1976

Some would have said that Severus was overdoing his revision for the practical part of his Potions O.W.L., as he was surely going to pass easily even if he didn't brew up something with his own improvements. Some indeed would have said he was overdoing it to revise at all, given that at only sixteen he seemed to be writing the book on the subject – or writing on a few books on the subject, anyway, to judge by the condition of his copies of Basics of Magical Brewing, Draughts and Elixirs: Theory and Method, and Advanced Potion-Making.

Severus, however, was determined to achieve top marks – over a hundred percent, if he could manage it. That certainly ought to impress... er... whomever he needed to impress. And to do that he needed to be prepared to make perfect or beyond-perfect potions. So although it was past midnight, Severus was still up, surrounded by books, reading and thinking and making notes. Normally someone of his year wouldn't be reading Advanced Potion-Making yet, but his mam had given him her thirty-year-old personal copy as a present on his fifteenth birthday. She'd said with a soft smile that she thought he might enjoy getting ahead on the material a bit, "since you seem to be taking after us Princes."

He tapped his finger on the page as he considered a recipe for a potion meant to aid the drinker in recovering memories thought lost in the depths of the subconscious. They weren't going to be asked to brew that at O.W.L., of course, but it was related to the simpler Sleeping Draught, which they might. Where the recipe for Sleeping Draught according to Draughts and Elixirs called for myrrh, the Recollection potion used its sweeter cousin opoponax, and Severus thought the substitution might sweeten the sleep, earning him a few bonus marks.

Laying Advanced Potion-Making aside for the moment, he picked up a slim book on the properties of aromatic resins which he had borrowed from the library earlier that day. As he leafed through it for the entry on opoponax, he came across a scrap of parchment covered with notes in an unfamiliar handwriting. His eye was immediately drawn to a circled word written sideways on one margin: Sectumsempra.

Severus mouthed the word silently and liked the feel of it on his lips. It surely had to be an incantation. He scanned the rest of the parchment, looking for mention of a wand motion or a description of the spell's effect. Some of the scrawl was obviously personal to whoever had written it ("Catherine, Friday, 6:30") and therefore meaningless to him. Other bits of it were illegible chicken-scratchings, or might have been legible once except that they were so crossed over and doodled around that he couldn't make them out. None of it explained what Sectumsempra did or how to cast it, nor was there anything to do with it on the two pages it was tucked between.

He leaned back against his pillow and thought about the word for a moment. He deduced that the spell had to have something to do with cutting or dividing, and in some sense doing it always, but the precise effect wasn't obvious; he could picture several slightly different possible results. Well, he could experiment with it later. He tucked the scrap of parchment into Advanced Potion-Making for later consideration and went on with revising for his O.W.L.

•·•·•·•·•·•·•

Early July

Severus was in his room, sprawled on his bed. You might have thought he was reading, but in actual fact he was in a funk so deep he could have given James Brown a run for his money. His eyes kept unfocusing to stare through the book's pages as a limited selection of sullen and angry thoughts about the day of his Defence Against the Dark Arts O.W.L. churned in his mind. Levicorpus... Mudblood... Save your breath...! Severus had been unable to get it all out of his head for three weeks and by this time he very much doubted if he was going to manage it any time soon. Normally he would be passing some of his time with Lily before her family went off on their summer holiday, but not this year; no, not this year. And probably never again, unless he could get her to change her mind.

He was startled by a scratching at his window. Severus's gaze shot up to the closed curtains. He had a sudden image of Lily hovering on a broomstick in the little yard behind the house, the twigs of its tail scraping against his window, and his pulse started pounding. Hopefully she wouldn't be so reckless as to actually do such a thing in broad daylight, but he clung to the tiny bit of hope – could she possibly have decided to come visit, even make things up between them?

Severus scrambled for the window, leaving his book where it fell, and drew open the curtains. To his dismay, all he saw was an owl, flying in circles and scratching his window on each pass. He hurried to open the window and the owl fluttered inside. "You feathered dunderhead!" Severus said in a harsh whisper. "You want my da to catch you? Who'd be sending me a letter anyway?"

The owl dropped a parchment envelope, which fell on his school trunk with a faint thunk as if there were a coin inside, and landed beside it. Severus picked up the envelope, which did indeed have some lumpy object inside it, and waved it at the owl. "Go on, bugger off! Tha'lt get nowt from me! Whoever sent you ought to know better!"

The owl scowled back at him as fiercely as he was scowling at it, pecked his hand hard, and took off again through the window, which Severus restrained himself from slamming closed. He pulled the curtains to, then turned the envelope over to read the address.

Lucius's handwriting. What on earth did he want?

Severus slid his finger under the flap of the envelope and opened it as he sat down on the edge of his bed. He pulled out the parchment inside and something slid out of it into his left hand: a silver disc, engraved with symbols and runes, attached as a pendant to a black leather thong.

Dear Severus,

Severus snorted at the notion of Lucius Malfoy, of all people, addressing him as dear.

I trust this letter finds you well as it leaves me. You will doubtless be aware from the Society columns of the better Wizarding newspapers that I have been making the rounds at some Ministry functions lately, in the company both of my father Abraxas and of Professor Slughorn. (He really knows quite a lot of important people, Severus; if you have not heeded my advice before, I again urge you to take advantage of that.) My father, naturally, intends me to eventually take over his position with the school governors, which will be an excellent opportunity for me. As you will also have noted (from the more scurrilous gossip in the Prophet) my offer for the hand of Miss Narcissa Black has been accepted and I look forward to shaping the schooling of the son she will someday bear me, and of course the schooling of many other young witches and wizards besides.

Severus sighed and rolled his eyes. Just listen to the prat! Twenty-two and already spouting off like he was lord of all he surveyed – although he supposed that wasn't such an unfair description given the sway he remembered Lucius holding in Slytherin house – and expecting the whole world to be aware of his every action.

As an observer of the work of the Governors I have seen good reports of your own prowess, despite the personal difficulties that I know you labour under. Therefore, I direct your attention to the enclosed artifact. I was able to obtain it by a few well-placed requests with certain Ministry personnel. I expect you have been irritated in the past with the restrictions placed upon you when you must return to that dwelling of yours every summer.

A smirk tugged at the corner of Severus's mouth. Restrictions, yes, but not so much as Lucius imagined; apparently he didn't know the real rules outside of pure-blood households. His mam being a witch – however little she might show it nowadays – meant anything he did at home was likely to be ignored by the Ministry, though dodging his da was a problem of its own since the man so rarely had work. Severus fondly remembered a day two summers ago when, as a result of an afternoon spent messing about with spells in the back yard, Lily had gone home with a teacup spelled to turn into a rat after a few hours had elapsed. A clever way of circumventing the way underage magic would normally get detected in a Muggle home, he'd thought. According to Lily's laughing report the next day, her sister – predictably – hadn't liked it one bit.

Next year I know you shall not be so hampered, but you will agree it is a sad thing to have to spend idle any time that might be employed in the honing of one's magical skill. Allow me to be brief:

"Allow"? Oh, why start now? Not that it seemed Lucius would know brevity if it got him by the short hairs...

The artifact is an amulet which nullifies the Trace placed upon its bearer. Whilst you wear it you may work magic as would any adult wizard and be assured no consequences will come of it – at least not on account of your youth.

Well, well! He could have done without the patronizing tone, but this was certainly interesting. There were things he didn't want to try at home, but he feared being caught performing his underage sorcery if he fared too far afield, especially since this was a Muggle neighbourhood.

Severus was annoyed, though not really surprised, that Lucius seemed to be discounting his wizarding parentage and the (admittedly small) freedom it gave him in his own home. He mentally fluffed his feathers and reminded himself that many of the Princes were every bit as pure as the Malfoys – so his mam had told him, anyway. He wondered, though, what had prodded Lucius into such risky generosity. Severus couldn't think of any service he'd performed to deserve this gift, nor anything he had of value that Lucius might be trying to bribe out of him.

Still, there was no denying such an amulet would be extremely useful. Curious, Severus slipped the thong over his head and slid the knots along until it formed a choker, the disc hanging just at the collar of his shirt. A strange tingling suffused him for a few moments, then dissipated.

Something was different. Intellectually, he knew what it had to be, assuming that Lucius was telling the truth about the effect of the pendant. In terms of his feelings, though, he was having a very hard time describing the sensation to himself. There was a coldness and emptiness to it, but at the same time it was exactly the same as he felt every day.

An uncustomary sense of adventure surged up inside him. If he could trust Lucius, and he hadn't got any sense that this gift was not what it was purported to be, then this would be a summer of incredible opportunity. To think of what he might practice or invent in private places away from his home where no one could disturb him! He knew he'd done well on his O.W.L.s, but one could always use more—

O.W.L.s. The thought stirred something in his brain, something beside the usual frustration and "if only"s he associated with the end of his fifth year. There was something he'd put away, meaning to revisit it... ah, yes! That spell on that scrap of parchment he'd swiped and stuck into his Potions book: Sectumsempra.

His stomach quivered with excitement. Well, no time like the present; Severus snatched up his wand and left the house as quickly and quietly as he could. There was still plenty of time before sunset, when he might be missed.

•·•·•·•·•·•·•

Not knowing quite what the results might be, Severus decided to try the spell on an inanimate object first. His feet led him to a certain shady spot by the river where he and Lily had often met and dreamt of the future, but despite his subconscious wish, he caught no glimpse of red hair through the greenery. He stood blinking for a few seconds as he saw where his traitorous heart had led him, and decided that a bit of rubbish caught in a branch dipping into the slow-moving river would be a suitable test subject.

He drew his wand out, aimed, and took a breath. He didn't know if there was some particular gesture he ought to be making, but he'd try just a straight pointing first.

"Sectumsempra!"

Nothing happened. Well, then, there must be a wand motion needed for this spell. It was clearly meant to cut, so Severus decided to try a movement that suggested that. He held his wand upright, and then—

"Sectumsempra!"

This time he waved his arm in a broad slash towards the plastic rubbish sack. A long gash tore through the thin material, ripping the bag entirely open on the side facing him and spilling its contents into the river. It was an impressive result given his clumsy and ignorant attempt, and a deliciously cruel thought occurred to Severus: what would happen if this curse were to be used on a living creature...?

He directed his wand towards the river. "Accio frog!"

He caught the unfortunate amphibian as it landed with a smack against his chest, leaving a slimy wet spot on his shirt. It croaked and squirmed with distress, but Severus quickly Stunned it. He set it on the ground, took a few steps back, and considered his aim.

"Sectumsempra!"

Frog blood sprayed across the ground, and Severus hurried forward to inspect the gruesome results. The frog's head would have been severed from its body except that the spine was intact. The spell had sliced through the frog's flesh like the proverbial hot knife through butter, but seemed reluctant to cut even its delicate bones.

He considered. He hadn't meant to kill the thing. At full strength the spell was apparently rather drastic. Might it respond to a throttling of magical power?

Severus Summoned and Stunned a second frog and sat cross-legged a short distance from it on the grassy ground. This time, he thought, he would just use a simple crescent-shaped flick of the wrist.

"Sectumsempra!"

Ah, interesting! Far from the animal being nearly bisected, a deep, clean cut welled up in its upper leg, spilling its lifeblood out onto the grass as Severus watched. This, he felt he should be able to heal. Confidently, he approached the frog and passed his wand over the wound, incanting a basic charm for closing small cuts such as this.

He was alarmed when after a couple of seconds nothing seemed to be happening. He was barely staunching the flow of blood, never mind knitting the wound. The frog was bleeding to death before his eyes. It was scary but fascinating, and suddenly he understood the "always" part of the incantation.

Severus silently caressed its sound-shapes on his tongue once more. What a beautifully sleek and lethal piece of spellwork this Sectumsempra was! He admired whatever witch or wizard had invented it, and wished his own creations to this point could have been as exquisitely awesome.

A dark flame of fantasy kindled in his brain, and his lips curved in a dangerous smile. How he suddenly longed to use this curse on one James Potter! But as appealing as that idea was, he didn't actually wish to kill the other boy. Much. No, before he could dare to try this new discovery on anyone human (at least he supposed Potter counted as human), a counter-curse was in order.

The sort of research that needed wasn't an easy thing away from the school's library, however. Severus owned only a handful of books on magic that weren't his school texts. He knew his mam had some more carefully hidden about the house, though she rarely got them out anymore; she must have years ago learnt off by heart the few things she now did. Severus couldn't remember the last time he'd seen his mam do more magic than make the draught that eased his da's asthma or set the dishes to washing themselves up. He reckoned the former was tolerated without comment because even a Muggle liked to breathe. The latter he could still recall some rows about from his childhood, but Da had apparently one day decided that it was easier to pretend it wasn't happening it than to continue to shout at his wife about it, as Tobias Snape would be buggered if he was going to do the washing-up himself.

As he walked home from the spot by the river, Severus took stock of the books he had seen in the house. In the end there was only one title Severus could think of in their meager collection that really dealt with healing, and if memory served him, it was rather basic. Still, it might provide a starting point.

•·•·•·•·•·•·•

Late July

Severus knew by this point in his life that theoretical reasoning could only go so far. At some point, one had to give in to practical testing. As he had no one else at hand to try the human effects of his Sectumsempra counter-curse on, the obvious subject was himself.

Although he was of analytical mind about these things, he was no masochist. He didn't relish the idea of slicing his own flesh open and – hopefully – mending it again. Yet his curiosity and his desire to add this spell to his usable repertoire outweighed his apprehension. So on a warm evening in August, having purloined a few tots of whiskey from his father's stash to give himself Dutch courage, he steeled himself for the attempt.

Severus settled himself on the floor of his room, back against the bed and towel beneath his leg. He stroked the Trace-nullifying pendant nervously, rolled up his trouser leg, and clutched his wand in his hand.

Careful, now, Severus; let's not fillet ourselves like a fish.

Severus lowered his voice to the barest whisper and pointed his wand at his left calf, ready to flick it in a small slicing motion.

"Sectumsempra!"

It looked as though he'd plunged the corner of a straight razor into his calf and ripped a gash about three inches long. It was surprising how little the wound hurt; clearly the spell was as sharp as the notional razor. There was a stinging, a surge of adrenaline, and then a metallic taste in his mouth as he watched blood well up in the wound and spill over.

For a moment he watched dumbfounded. There was so. much. blood! And from such a relatively small cut! But he was here to do something – to try his counter-curse. Mustering his wits, Severus pointed his wand at the gash and recited the incantation he'd devised.

Nothing happened.

Oh, God, it doesn't work; it doesn't work!

He started to panic. Had he just fatally injured himself? Had he managed to hit an artery? No, that couldn't be; were there major arteries in this part of the leg? Even if there were, wouldn't this wound be spurting rhythmically if that were the case? No, no, he couldn't have hit something vital. It looked like a lot of blood, but it couldn't have been more than a quarter – a third – a half a cup – oh, God, he didn't know, but he was feeling lightheaded at the sight of it.

In desperation, not knowing what else to do, Severus started to trace his wand up and down the edges of the wound in his leg. Blood glistened on the tip as his voice turned singsong in his shock and delirium.

To Severus's surprise, this actually helped. The wound seemed to respond to the musical sound of his voice, and he repeated the limping melody line more and more strongly, becoming a soft singing chant, as the wound began to knit before his eyes.

Finally, it was over. He'd made quite a mess of the towel he'd laid out underneath him; fortunately he'd not been sitting on the bed. Severus slumped back against the side of his bed, laughing in quiet hysteria. Nice one, Snape! Wouldn't that have been an amusing end if you'd picked somewhere more vital?

He touched a hand to his mouth as he laughed, and tasted blood on his fingers. He stood up, still a bit wobbly, and steadied himself against the chair pushed against the table underneath the window that served him as a desk.

Turning his head to the side as he breathed deeply, Severus caught a glimpse of himself in the glass of a small, grimy mirror whose frame was nailed to the wall. His grey curtains made his room a sort of cave, a place of artificial twilight which softened his complexion and the angles of his face, framed in the black falls of his hair. A spot of blood was visibly dark on his lower lip, and he snaked his tongue out to lick it off as he stood strangely transfixed by his own reflection.

He approached it as if in a trance. His cheeks were slightly flushed, his hair a bit mussed, his pupils quite dilated from the rush he's just experienced, both magical and physical. The top couple of buttons of his shirt were open, and a sheen of sweat glistened on the skin of his throat and upper chest. He swallowed and watched the movement in the hollow of his throat, seeing Lucius's Trace nullifier hanging there, the black thong dark against his skin. His lips were slightly parted; one corner of his mouth quirked at the absurdity of it all.

As he gazed at this Severus in the mirror who was so different from the one in his head, he began to feel a deep, hot, sweet ache in his loins: the pleasure of the power of magic, the power of this beautiful (...what? had he just thought that?) dark wizard he saw in the mirror, the one he must be in his own future. Who was the fairest of them all? Snow White he was not, hair as black as ebony notwithstanding, but it didn't matter. Between the lingering caress of the Dark magic still inside him and the sight before him, he was quickly becoming so powerfully aroused that it almost hurt.

Groaning, he fell back onto the bed and couldn't get his hand down his pants fast enough. He felt it, he knew it. Thin lips parted in a gasp, dark eyes slid closed, slim his writhed and bucked upwards as his hand sought his cock. And if he thought all this so hot – then what of Lily? How could she resist a wizard like that?

Uncomfortable now in his clothing, Severus tried awkwardly to wrestle himself out of his shirt. He managed to undo most of the buttons and push down his trousers and underpants with his off hand, but wasn't sure how to get the sleeves off his arms. For a moment he knelt, shirt hanging open, cock standing proudly out of his fly and cradled in his hand. Frustrated, he finally let the shirt hang uselessly on his left arm as he forced his right hand to slow down.

He still stroked himself hard but not as desperately, although he could tell it would barely slow the oncoming orgasm. The silver pendant dangled between his collarbones as he leaned forward, pushing his cock into his own hand, pretending it was Lily, feeling her yielding to him, loving him, awed by what he'd done. Such sweetness, such pleasure from the dark coil of the new magic inside him—

Severus turned his face into his arm and bit skin and cotton to muffle his cry of pleasure as he came.

•·•·•·•·•·•·•

As he came back to himself, he frowned at the streaks of semen on his thin duvet. He sat back on his heels, panting, sure he made quite a picture now, clothing all askew and hair even more tossed about than it had been when he'd seen the reflection that prompted all this. With a grimace, Severus fished his wand off the floor and Vanished the mess. Then a wry grin crossed his features at the thought of this most prosaic use for Lucius's gift: why, he could clean up after himself anywhere and no one would ever know!

He straightened his clothing as he got off his bed, and vaguely it came back to him what he was supposed to have been testing. Fishing his Advanced Potion-Making book out of his trunk, he flipped to the page where the scrap of parchment bearing Sectumsempra was stuck, and snatched his self-inking quill off his desk. He copied the spell onto the margin of the page where the scrap was inserted, then paused.

Now that he had a workable counter-curse – though apparently it needed practice – what should he say of the spell itself? Knowing he could fix the damage, he no longer felt so apprehensive about applying it to Potter. He pursed his lips in thought, then grinned more widely than he had in some time. He made a notation underneath the incantation – For enemies – and closed the book on the barely-dry ink.