Disclaimer: I own none of the recognizable characters appearing in this story. They belong to J. K. Rowling, and I am making no profit from this fanfiction.

Summary: Harry wanted to defeat Voldemort. That was the only thing he wanted. He really couldn't have known that accepting the aid to do so would bring about not only war in the wizarding world, but revolution.

Pairings: At this point, I really don't know what pairings there might be, or if they would be het or slash. I have most parts of the plot laid out in my head, but romance is something I have to improvise. The only thing I can say with safety is that this will be a fairly lengthy story, and mostly plot-driven.

Rating: R for violence, gore, torture, language, and character death.

Timing: It begins the summer immediately after Harry Potter and the Order of the Phoenix.

The Unforgivable Wars Book One: Imperio Chapter One: The Power the Dark Lord Knows Not

Harry Potter was used to waking from nightmares. This one was different. He woke into a nightmare- the pressure of sharp teeth on his right eyelid, and a voice saying, "You do not need both eyes, do you?"

Harry lay still, barely breathing. Anger might have overtaken him if he let it. Sirius gone and Voldemort back; didn't he have enough to worry about? But fear overpowered everything he might have said when the teeth shifted slowly along his eyelid, prickling and punching at the skin.

"Good," said the voice. Harry listened for breathing, but heard none. He couldn't feel breath on his face, either. He pictured a vampire crouched over him, fangs resting on his eye, and fought the temptation to be sick. A vampire couldn't get through the wards on the house, could it? I thought Dumbledore said I was safe here...

The voice snickered. "Not safe from us," it said. "I am not Voldemort. But we are something you should be wary of. Oh yes, Harry Potter. Very cautious. Very frightened." It giggled, a sound that reminded Harry far too much of Bellatrix Lestrange in the Department of Mysteries, and shifted to the left, so that the teeth rested mostly on his cheekbone.

Harry took a deep breath and summoned all the anger he could, then heaved himself off the bed. The thing went flying away from him with a snarl, and Harry scrambled off the bed and for the loose floorboard where he'd hidden his wand. He should have kept it by him, he scolded himself as he knelt frantically and rummaged for it. He should have-

A massive weight hit his back, pinning him to the bedroom floor and knocking the wind out of him. Harry grimaced as his mouth hit the floor and began to bleed.

"What do you want?" he hissed, fighting the temptation to shout. That would bring the Dursleys upstairs in a minute, and any Order members watching the house, too. Harry didn't want them there. He hadn't wanted them in his room all summer, and that wasn't about to change until he learned that he couldn't fight the thing on his back by himself.

"To help you," said the thing.

Harry laughed bitterly. "Of course you do. Why'd you bite me and try to kill me, then?" He attempted to move, but the thing seemed to grow arms and pin him down. Harry didn't bother trying to turn his head to get a good look at it. It was almost mashing his lip into the floor, too.

"I do want to kill Voldemort."

Harry looked up immediately. There was something else in front of him, but it merely prowled out of the shadows and sat watching him in the fall of moonlight from the window. It looked, Harry had to concede, like a cat, though a very large one—it would probably reach his waist if he was standing up—and with white patches on its black fur that rippled and moved strangely, as if they were patches of moonlight on the surface of the lake at Hogwarts. Harry swallowed when the cat bared its teeth. Those were the sharp things he had felt on his face, he was sure, more like needles than teeth.

"What are you?" he thought to ask, finally. Maybe that was better than asking what they wanted. Maybe they would give him an answer that made sense.

"We are me," said another voice, and a second cat came out of the shadows to his left.

"We are the ones Voldemort disturbed." A third cat was sitting to the right, though Harry hadn't seen it move. Its eyes were larger than the others', and glittered golden. "The ones he woke because he was always seeking for power, power, power." It bared its teeth and giggled just like the one on Harry's back. "And he found it. Just not the way he thought."

"I am the power the Dark Lord knows not," said a fourth voice from behind him.

"We are all the power the Dark Lord knows not," said the voice in his ear, and giggled loudly enough to hurt. Harry tried to rub his ear, and found that his arm was still pinned to the floor.

"And you just decided to show up now?" he demanded. "And why are you cats? And what the fuck is going on?" He felt a brief blaze of guilt at using the word, but then told himself he didn't bloody well care. Who was going to hear him? The Dursleys would only wake up for screams, and the Order members didn't care, and Ron and Hermione certainly weren't there to hear him. Their letters had been distant and filled with vague hints. The most expansive ones he'd gotten from them were on his birthday, and they'd been only a few lines long each.

The cat on his back leaped off, and padded around in front of him. Harry still couldn't feel its breath as it leaned down and shoved its teeth near his face. "I could show you what we really look like," it said. "Unless you are frightened of me."

"No," said Harry, resenting them all fiercely. He wondered if he could get his wand and fling them across the room with a curse before they could move—

The cat vanished. In its place was intense blackness, and a searing cold, and something so horrible that Harry shut his eyes instinctively and tried to back away, slamming into something else cold as he went.

He couldn't feel anything else, as his fingers tingled and went numb in the next second. He couldn't even feel the floor anymore. He was hovering in darkness, and a wind shrieked in his ears, and someone very far away was laughing and would not stop, and something near was buzzing like a hundred flies, and—

Abruptly, the cold vanished, and Harry found himself slammed into the floor again. He opened his eyes, shaking, to find the nearest cat lying almost nose-to-nose with him. Its eyes were intensely green.

"Lie still," said the cat, almost gently. "We will tell you my story, but you must listen, and you must decide if you wish to make an alliance with us in all good faith."

Harry nodded shakily and rubbed his head. What is going on? Probably just something else that Dumbledore forgot to tell me, he thought viciously. But he seemed stuck in the room for right now, and no one had come pounding up the stairs to save him, so he might as well listen.

Besides, a tiny—tiny—glimmer of hope was growing inside him. If these things really wanted to kill Voldemort, and Voldemort didn't know about them, then maybe they really could help him. Harry had gone almost mad this summer, lying in his bed, having nightmares about the tortures that Voldemort performed steadily, and completely unable to learn anything that might let him help. He had even written Dumbledore asking if he could come to Hogwarts early and get some kind of special training that would let him go up against Voldemort. Dumbledore had answered him, kindly but sternly, that winning the war wasn't Harry's responsibility alone, and that owls could be intercepted, so he should owl only when he truly had need, and only in code.

The green-eyed cat went on speaking, while the other four lay down, staring intensely at Harry. Harry tried to ignore the stares, though they felt like the ones aimed at his scar all the time, and fixed on the green-eyed cat. It seemed to know what it was talking about.

"Voldemort, who was once Tom Riddle, has traveled widely all over the world," the green-eyed cat began. "This much I learned about him, when we rose at last."

Harry opened his mouth, then hesitated.

"You may speak," said the cat, in a voice that reminded him almost of Professor Lupin.

Harry nodded. "Why didn't you know about him before?" he asked. "And why do you keep speaking that way?"

"What way?"

"Well—leaping back and forth between we and I," said Harry, wondering if he should have mentioned it now. It was a small thing. These creatures were willing to help him. He wanted help, didn't he?

"That is the way that I am," said the cat. "The way we all are. No difference. Do you see?"

Harry didn't, but he just gestured for the cat to keep talking.

"I did not know about him before," the cat continued, "because we had no reason to. He tampered with the Dark Arts, but that was all they were. Dark Arts, not the Darkness. Cruel little spells that you humans use against each other, and not any powers that lie in the night." Its tail flicked, once, and Harry saw its eyes change color, dancing with the moonlight. But they returned to green in the next moment, and the cat lifted its head as though it regretted having changed in any way. "Of all your spells, only the Unforgivables come close to the true Darkness, and even they have been warped and changed. So long as your Tom Riddle played in the shadows, I had no reason to wake from our slumber.

"But then he touched the Darkness. Oh, he dared." The cat hissed, and its hiss was echoed by the other four. Harry shivered, for a moment feeling that cold wind play around him. "He dared to come back from beyond death, to invoke the magics of immortality that lie in the Darkness and pretend he had a right to them. No human does that. I awoke, then, and tried to kill him. But he had your blood. He has played games, this Tom Riddle, this Slytherin snake, this shadow-dancing fool." It bowed its head, and Harry had the disquieting sensation that now all the cats really were staring at his scar. "He has set up what he thinks is a private game between the two of you. Kill or be killed, is it not?"

"Yes," Harry whispered, remembering the prophecy. And either must die at the hand of the other for neither can live while the other survives…

The cat nodded, an oddly human gesture. "He thinks to set himself beyond any vengeance. He does not know of us, but he would break your protection and prevent anyone else from interfering in the game. I must enter the game to stop him." Its head twisted to the side, and Harry became convinced that it was going to fall off, but the neck seemed to stretch and bend, flexibly, so that the cat could look at him sideways. Of course, it wasn't really a cat, Harry reminded himself, and swallowed the queasy feeling in his stomach. "In one way, his shadow-dancing has protected him," the cat mused. "There is no place for the true Darkness in such shadows, not unless we make one. I have come to make one."

It stood up, quite abruptly. Harry would have backed away, but there were the other four around him, waiting. The green-eyed one stepped forward, gaze on his scar and then on his face.

"Harry James Potter," said the cat, and Harry's skin prickled worse than it had in the cold wind of the beings' true presence. "We formally request entrance to the game."

"How?" Harry asked. His voice croaked, and he fought off the urge to wrap his arms around himself. He had to be strong. They're offering me a deal to defeat Voldemort. They're part of the prophecy. I have to listen.

"I will enter your body," said the cat. "All of us will, turning into Darkness and passing within. Through you, I may defeat Voldemort—for though he has your blood in his veins and so has sealed himself against other enemies, he has no protection against our might passing through your hands, your eyes, your wand." It paused, and its eyes went back to Harry's scar again. "Your magic," it added in a whisper that nonetheless made the floor tremble. Harry hoped the Dursleys wouldn't wake up now. "I will give you magic, Harry, magic such as you have never dreamed."

Harry licked his lips. He wanted to. He wanted Voldemort dead, and he wanted the Death Eaters dead, and he wanted Sirius back—but that wasn't going to happen. Was it?

"I thought the Darkness wasn't for humans," he ventured.

The other cats giggled. Harry flinched. Their laughter really was too high and piercing. He wondered if he would become used to it.

"It can be, if we let it be," said the green-eyed cat. "I shall give it to you, Harry. In return, we shall live in your body, and defeat Voldemort through you."

Harry shuddered as he remembered the way that Voldemort had possessed him in the Department of Mysteries. This was the same thing, wasn't it? It had to be bad, didn't it?

"It will take some time," said the cat, as if listening to his thoughts. "But I may give you a taste of it."

It leaned forward, and touched its tongue to his scar.

Harry jumped. Quite suddenly, the room around him had vanished, and he stood in a ring of stones. He glanced about quickly. He had been here before, in dreams, and knew the barren branches of the trees that leaned over the stones. The Death Eaters killed Muggles here.

"You are quite safe, Harry," said the cat's voice beside him, and it stepped into view, its body transparent. Harry glanced down and noticed for the first time that he himself was transparent. Around him, other shadows flickered and darted, and he guessed those were the cats, moving into place. "We will protect you. And I will give you what you most want. Look ahead of you."

Harry did, and felt his heart contract. A woman had just stepped into view between the stones, smiling and mad. Bellatrix Lestrange.

"She is yours," said the cat beside him. "Do you accept our bargain, she will die screaming in agony this very night."

Harry hesitated one more time. This talk of Darkness and moving inside his body rather frightened him—

And then he saw Sirius again falling through the veil, stabbed by the red light from Bellatrix's wand.

How could he give up the chance to avenge Sirius? It was what his godfather would have done for him. Besides, wasn't he supposed to accept this power? They were "the power the Dark Lord knows not." They were part of the prophecy.

Bellatrix Lestrange laughed, just the way she had after she killed Sirius, at something another Death Eater behind her had said, and Harry made up his mind.

"Yes," he murmured, unable to take his eyes from her. "Oh, yes."

There came one more chorus of shrill giggles, and the green-eyed cat's voice said, soothing and low, "You shall not regret this, Harry James Potter. So the bargain is sealed. Tenebrae!"

And the Darkness came into Harry.