This is a one-shot! No longer. So it shouldn't interfere too much with my ongoings. Okay? Just an idea. HBP compliant. Final battle. Enjoy.

Disclaimer: I don't own HP. And Severus' quote, I found in an author's profile and loved. I don't remember who it was, so if you're reading, sorry for borrowing, and I hope you'll forgive me.

Poison & Purify

The Dark Lord had a thing for graveyards. Maybe it was an attempt to keep up the whole 'Lord of Darkness' image, which could be difficult when it was your enemy who had the huge, imposing castle. Maybe it was a repressed urge to be close to family. Or maybe it was just a morbid fascination with death. Whatever the case, Severus felt that, from a tactical point of view, he really could have chosen a better site to battle his enemies. A graveyard is fine for dark rites and skulking, but for pitched battle, the broken terrain was a decided nuisance for the Death Eaters. However, since what Severus personally needed to do was skulk, it was fine by him.

While curse-lights flared overhead and all around him, he slipped through like another shadow in the gloom, silently sending a wry thank you to the Marauders for all their help in perfecting his stalking abilities. He ignored the battle around him, intent on his prey. And there they were. Back in among the mausoleums, away from the open battle in the less cloistered areas of the graveyard, engaged in their own private, prophesied duel. Potter and the Dark Lord.

Resting for a moment under the eves of one of the more elaborate tombs, Severus watched them critically. Potter was doing his usual thing: running around, dodging and diving behind tombs as if he were in the air over a quidditch pitch. Voldemort was relying on slightly more Slytherin tactics, moving from vantage point to vantage point and sniping at the restless Gryffindor. Severus sighed. Typical. At this rate, it'd be hours before either of them even hit the other, what with Potter moving too fast for the Dark Lord to strike, but also too fast to allow himself to aim properly. The way they were going at it, the only way one was going to win was through luck or sheer bloody-minded persistance. It was lucky that he had a more elegant solution, then.

Step one: from hidden vantage point, get in a shot at Potter's leg as he goes by.

Step two: surreptitiously charm his wand just that little bit out of reach, and wait for Voldemort to take advantage.

Step three: watch and wait for your moment to step in.

Smirking, Severus watched as the Dark Lord, seeing Potter's fall, stepped into the open to gloat. Potter scrabbled furiously for his wand, but a quick immobilus let Voldemort stand back and survey him at his leisure. An already inhuman face further twisted by a sneer gave Voldemort a demonic look as he sized up his prey.

"Crucio," he murmured sibilantly. Severus winced as the boy screamed, but the sound soon died when the spell wore out, perhaps a touch faster than usual. A slight frown appeared on the Dark Lord's face, and he repeated the spell. This time, the dissipation was noticably faster. Potter looked up in pained surprise as Voldemort stared incomprehendingly at his wand, wondering what was wrong. Then, snarling furiously at the attack's ineffectiveness, Voldemort spat the killing curse. Green light arced out of the wand, towards Potter's terrified face ...

...And died, sputtering out well before reaching its destination as its caster crumpled forward onto his knees. Even the immobilising spell holding the boy in place disappeared. Even though he was shocked, Potter lost no time in leaping to his feet and retrieving his wand, holding it in shaking hands as he stared at the gasping Dark Lord in wonder. And Severus stepped forward from the shadows.

"Feeling a bit weak, are we?" he sneered, head to one side as he studied the fallen Voldemort with a scientist's cold gaze. Disguised behind that dispassionate stare, the potions master allowed himself a brief frisson of relief. There'd be a moment, when that first torture curse had been cast, when he'd feared that it wasn't going to work ...

"You!" Voldemort gasped. Severus smirked.

"'Oh, don't look so surprised,' said the reptile with a grin, 'you knew I was a serpent, before you took me in.'" he quoted, the sneer more prominent than ever. But it was true. Voldemort should have known better than to trust a man who'd thus far seemingly betrayed everyone who'd trusted him. But he'd counted on the man doing just that, because, like Albus, in many ways Tom Riddle was an innocent soul. For all his posturing, and his division of his soul, the Dark Lord was still human, and like all humans he needed companionship. He'd needed to trust someone, and Severus had simply made sure it was him. In some ways, it had been disgustingly easy to entice the man into trusting him, and blinding him to his true intent.

Potter was wavering, looking from one of them to the other, wand involuntarily following his head's movement. Severus could understand his confusion, looking at an incapacitated Voldemort, and a traitor who'd apparently done the incapacitating. He'd counted on that too, to give him the chance to step out here and say his piece without the trigger-happy Gryffindor cursing him from here to kingdom come on instinct.

"I do apologise for interfering, gentlemen," he began. "But there are a number of things about this situation you should probably know. Firstly, and most importantly, you're dying, Riddle. It's already begun, and if the weakness has already taken hold, then you've maybe an hour to live. So sorry to be the bearer of bad news."

Voldemort, greying complexion gone bone pale, stared at him in rage. "What have you done, traitor?" he hissed.

Severus squatted down to look him in the eyes, the cold, measuring gaze back in force. "It really is one of my most elegant inventions," he murmured. "A truly beautiful poison. Compiled from some of the rarest ingredients, and some of the most ridiculously common ones, brewed into a gorgeous cocktail that has no antidote. Nothing, not even a beazor, can help you now. But we have a choice, here. And in this choice lies the true beauty of my work, my Lord."

Still crouched, Severus slanted his head to look at Potter. Hypnotised, Riddle followed his gaze, staring desperately at the boy. Potter took an unconscious step back, confused and not a little frightened by the turn of events.

"Left alone," Severus continued, holding Potter's gaze, "the poison will run its course slowly. It's an incendiary, and will focus on your nervous system, slowly burning you up from the inside. A rather ugly way to go. However, and here we come to our dear Mr Potter, if the poison were to be helped along, say by a well placed killing curse, then you would die immediately, cleanly, and the poison's fire would reach out through the mark, fueled by the death-curse, and destroy every Death Eater you ever branded. Your entire legacy would be destroyed, but you yourself would die without the torment my poison would otherwise engender."

He turned back to stare mockingly into Voldemort's desperate red eyes. "What do you think, my Lord?" Severus whispered. "Is it not the perfect poison? What shall we choose, my Lord? Shall you preserve your legacy, and let all those mewling sycophants keep their worthless lives while you drown in the agony of fire, or shall you embrace a clean death and abandon them to their fate? What to choose? It's difficult, isn't it? I know. How about we let our wonderful Mr Potter choose for us? Hmm?"

Severus stood, smiling darkly at the horrified boy. "After all," he continued conversationally, "he is the one who is destined to cause your death. He is the one whose efforts have destroyed all your pretty Horcruxs, leaving you with no way to avoid death. He is the one whose entire life has been a quest to see you destroyed. I think he should be the one to choose, don't you?"

Harry stared at him, the wand now fully focused on his brooding figure. Severus stood relaxed, arms folded, making no threatening gesture, but he knew his very presence was a threat in and of itself. His entire figure seemed to radiate leashed menace. He knew this. He'd made it so.

"You're bluffing!" Harry burst out. Severus raised an eyebrow, the gesture a needle to spike the boy's anger. "You've got the Mark too! If it worked like you say, if I killed him, I'd kill you too! You're trying to stop me from killing him! You're lying!"

"Am I?" he murmured laughingly. He could see Potter hesitate, and a brief flicker of worry shot through him. It all came down to Harry now. His entire scheme hinged on the boy taking the path he'd expected. It was his future that hung in the balance here. The Dark Lord was dead either way. What Potter chose decided his fate. He'd done everything he could, now. He didn't think the boy would risk it, but there was that doubt. That niggling doubt ...

It was Riddle who decided the matter. Furious, incensed by the fire he could already feel eating his insides, the Dark Lord lunged to his feet, determined to take the traitor with him. He leapt. Severus swung to face him, laughing in surprise, and a lance of green light hammered his attacker out of the air.

For a moment, Severus was blinded by the afterimage. Unable to see, he spun towards Potter's sudden scream, staggering in that direction even as his vision grudgingly cleared. The boy had collapsed, writhing on the ground, clutching his forehead. Severus knelt beside him, catching his head and holding it still between his palms until the shudders and the gasping screams had ceased. Then, panting, Potter lowered his hands, to bare a clean, unmarked forehead. Severus blew out a breath in relief.

"It worked, then," he marvelled, tracing the place where a lightning-shaped scar had once existed. He laughed. "It worked!"

Harry stared up at him in shock, completely blindsided by his apparent delight. Severus drew one of the boy's hands up to see the cause for himself. Potter frowned in bewilderment, then gasped as his fingers encountered unmarred skin where before there would have been a raised welt of scar tissue. For a moment he could only lie there, hand to his head, shocked and awed.

Then the screams reached them. Potter jack-knifed upwards, nearly smashing his face into Severus', and leapt over to stare out between the tombs at the horror of the battlefield. Lurid moving flames licked at the sky, their crackle drowned out by screams of agony. The Death Eaters were burning. Severus moved behind him to watch. Strangely, he felt no satisfaction at the sight, only weariness and a vague sense that he'd finally accomplished his goal. The war was over. Soon, he'd die too, and wander out of this stupid life to say hello to Albus, and find that dumb mutt so he could castrate the bastard for being so stupid. Harry'd chosen right.

Harry, horrified, spun to face him. "You ... You weren't lying! It really is killing them! You weren't lying!" He slowed, repeated himself. "You really weren't lying."

"Yes, Mr Potter, I believe we've established that," Severus said wryly. "I really wasn't lying. What a change, hmmm?"

"But ..." Harry tried. "But if you weren't lying ... Your Mark! Are you ...?"

Severus rolled up his left sleeve. The ugly brand lay nestled under his elbow, where it had plagued him for nearly a quarter of a century, its livid face now decorated with little greenish flames. They ran across his arm, lapping playfully at the evil sign, looking eerily beautiful. For some reason, they hadn't spread, and he was in no pain. There was simply a delicious tingling in the arm. But the potion that burned inside the Dark Lord's body was working, spreading its cleansing fire out to him. However, it was being strangely slow ...

He frowned down at his arm. "What's wrong?" he muttered angrily. "You work. I know you work. Why are you being so slow? What's wrong?"

"Nothing's wrong, Severus." A new, damnably familiar voice chuckled at him. He saw Potter's awed, desperately hopeful expression, and turned in resignation to face the Headmaster.

"Albus," he sighed. "What are you doing here, old man? You're dead." He glared pointedly, and hoped the old man would take his meaning and leave. He did not need this right now.

"I came to see you, my boy. And Harry too. I'm so proud of you, children. I'm so very proud of you." A ghostly tear trickled down past a beaming smile and into the old man's tangle of a beard. Severus rolled his eyes at his obvious joy, feeling the sharp spike of guilty regret for killing this innocent man. It had been necessary, critical even, but that hadn't made the act any easier to carry out, or the guilt afterwards any easier to bear. At least the being who'd made it a necessity was destroyed now. Riddle was dead. That, at least, had gone as planned.

"What do you mean, nothing's wrong?" he demanded irratibly. "It isn't working as its supposed to. It hasn't killed me." Potter gasped as he realised what that meant, that Severus had intended to die, but Albus only grinned.

"I said nothing's wrong, my boy, and I meant it." The twinkle was only more obvious in the ghostly versions of those blue eyes. "You were defeated by your own genius, Severus. The potion you designed, your lovely poison, was exactly as you intended. You succeeded. You created a liquid manifestation of phoenix fire, as you planned. The fire that can never be doused, and burns pure all touched by evil. Triggered by the evil of a conscious decision to take a life, and transfered through the evil of the Mark, it destroyed the Death Eaters as you planned. But you failed to account for the phoenix's nature in relation to yourself. The fire only burns to purify. Those who are evil, who turned to it willingly and enacted it with joy, are destroyed. You, who turned away from it, who fought against, who was willing to give your life to destroy it, are no evil being. Your fire burns the mark of evil from you, but it cannot burn you. It cannot kill you. You forgot. Your poison has no antidote, save your own inherant goodness. Your own purity."

Severus squeezed his eyes shut as the old man's words rolled over him. The words of the man he'd murdered. He hadn't forgotten. He'd simply been sure that the taint of evil within him, the taint left by his own decision to take an innocent life, would have been enough to enable the fire to destroy him. He'd been so sure ...

"Severus," Albus called gently. "Severus, you've had your trial by fire. You've lived for twenty years in the fires of retribution, trying to undo the evil you thought you had commited. You've spent twenty years purifying yourself. It's time to step out of the ashes of that fire. It's time to be reborn, Severus. Your phoenix fire has taken the last taint of evil from you. It's time to live, my boy."

The warm, loving voice faded slowly. Severus knew that when he acknowledged the truth of what had been said, Albus would have completed his last task in this world. He'd seen Harry safe, and if Severus but said yes, he'd have saved the man who killed him too. All Severus had to do was forgive himself the same way, and Albus would be free to go on the 'next great adventure', as he longed to do. All Severus had to do ...

He laughed softly, shaking his head in wonder. Meeting the ghost's gaze, he laughed. "Ah, old man, how very Slytherin of you. I've little choice, haven't I? If I refuse, I condemn us both to the fire, don't I? Ah, the elegance. The choice that is not a choice. Very well. Very well, Albus, you have your wish. I will acknowledge the evidence my own creation gives me. I'll say the words you want to hear, and mean them."

He stared into the ghostly eyes, a gentle smile playing on his lips. His eyes were laughing. "I forgive myself, Albus," he whispered softly. "I will live. I'll let myself be reborn, and make new choices. I forgive myself, do you hear? Now begone, you damned meddling old man. Go on to your wonderful adventure. Begone, and leave us living in peace. Do you hear?" He laughed.

Beside him, Harry looked from one face to the other, then slowly smiled too. He looked to Albus aswell, and gravely added his promise to live. It was important to the old man, Severus knew. More than anything, Albus wanted to see them free, not just from this war, but from the choking grasp of their own tangled consciences. He wanted them to be free to make fresh choices, based not on harsh necessity, but on their own heartfelt desires. It was the old man's last wish, and they would honour it, if only to be rid of him.

Albus left them his blessing as he left, fading from them to join all the children he'd lost. Eventually, Severus would follow him. Eventually, Harry would too. Eventually, everyone would. Eventually. But first, they had lives to live. And on that note ...

The clamour as the Order searched for their Golden Boy, and the cause of the Death Eaters' sudden deaths, grew louder. They were approaching fast. Severus turned to Harry. "This is where I disappear, Harry. I've no interest in being reunited with all our angry friends. Do give them my best wishes, won't you?"

"Where will you go, sir?" The boy ... the man asked. Severus smiled.

"Why, wherever the hell I feel like, Mr Potter! Wherever I want. Have fun being the hero of the hour, Harry. But if you'll listen to my advice, listen to this. Don't count on it lasting. Albus, rest his soul, lived trying always to be the hero he was in the Grindelwald wars. Don't make the same mistake. Live as you want to live, not as you're expected to. And maybe I'll see you sometime."

Harry nodded. "See you around, sir. Enjoy Hawaii, or wherever you decide to go."

Remus Lupin burst out between tombs to the sound of Severus' laughter, but the potions master was confident he'd caught no sight of him as he'd apparated out. A rush of random apparitions later, and Severus stood on a cliff, staring out at the waves as he laughed until his ribs ached. He stretched his arms wide as if to embrace the world and laughed.

Freedom. Glorious freedom. The world was his to walk as he chose. There was no war, no duties, no Dark Lord, no guilty remembrances to bind him. He could go wherever he liked, do whatever he chose.

Hmmm. Hawaii actually sounded pretty good. For a start.

Well? I decided to give it the happiest, and most realistic (sorta) ending I could think of. What do you think? R&R and tell me.