The last thing I thought of when I started this OneShot was writing smut. I merely wanted to analyse the love/hate relationship Bellatrix and Sirius shared. The sex part came as a surprise for the characters as it came for me. But it happened. Now live with it. Or don't read the story.

Equals

The night was starry and ice cold, just like Sirius loved it. Once again he had escaped to the roof of number 12 Grimmauld Place, the only place he wasn't forbidden to go to and Sirius was sure that if his friends had known he was up there every night, they would prohibit that also. The only company he had was a bottle of Firewhiskey, or so he thought. A few times Sirius had stood on the edge of the roof, wondering what it would be like to fall and hit the ground. Would he live long enough to feel the pain? Those moments of suicidal thinking were rare, for drunk he always lost the courage to actually jump. After all, a life as prisoner was better than no life at all.

Tonight, however, was different. Tonight he was not filled with bitterness. No, apart from blood and alcohol a different venom was running through his veines, poisoning his heart and thoughts. Hate.

Bellatrix Lestrange, his cousin, a famous Death Eater had escaped from Azkaban and was now on the loose, free to go her usual, cruel ways. And cruel she was. Always her wand at the ready, prepared to fire away her favourite spell: the cruciatus curse. In their youth Sirius had experienced what it was like to be hit by that curse on several occasions and Sirius was sure that Bellatrix still had that little scar on her shoulder he had given her in return. Yes, they had hated each other from their early days, even before they had started school and were sorted into different houses. But it was not the differences that had made them enemies for life, it was more the fact that they were as alike as two people could possibly be.

They were equals. Unstoppable in their determination to fight for what they thought was the right thing to do, passionate, headstrong, hot tempered. There was no magic one of them conjured that the other couldn't counteract. Even the foulest tricks Bellatrix used, they weren't enough to beat Sirius. And when he thought he had found a spell that could knock her out, he was so much mistaken as one could only be. After a while, Sirius found it hard to admit, he had come to love their hate relationship and the constant challenge that came with it but he realized that their childish games had ended the day Bellatrix joined Voldemort.

Suddenly the realisation why this night wasn't like any other struck Sirius like lightning and he turned around to see who was disturbing his solitude. And there she was emerging from the shadows; a tall woman with wild, black hair, wearing a torn dress that had once been handsome. He only recognized her because Sirius knew how people changed in wizard prison.

"Missed me, dear cousin?" Bellatrix asked as he watched her moving closer.

"Most certainly not," he said in a calm voice. It was a lie. He had missed their fights.

"Stupefy!" Bellatrix cried before Sirius could even reach his wand. He had no choice but to jump out of the way. "Liar!"

"Cheater!" He called back.

Bellatrix lowered her wand. "Where's the fun when you play according to the rules?"

Now Sirius grabbed and raised his wand, calling "Stupefy" and causing Bellatrix to fall backwards. Oh yes, he had missed her.

"I hate you," she cried while she got to her feet again.

Sirius laughed as if she had said something very flattering. "I can only return that compliment."

For the first time in months Sirius felt alive and happy to live but Bellatrix had always had that effect on him. The hate pumped adrenaline into every cell of his body, giving him a strength he could never reach in any other fight. Bellatrix was his equal. She made him complete in a very twisted way and Sirius had always known that she felt exactly the same.

And now they were fighting on the roof of number 12 Grimmauld Place, just like in the old days, sending curses at each other, sometimes missing, sometimes striking. Sirius knew that it could go on like that for hours if one of them didn't give up (an absurde idea) or died (more likely). It was an old agreement they had made in their teenager years that kept them from using Unforgivables or spells that caused great damage, like Sectumsempra but Bellatrix was the first to break the tradition by sending a Crucio at Sirius. Luckily he ducked at exactly the right time and stunned Bellatrix who fell to the ground once more, letting go of her wand.

Sirius walked over to her and stood triumphantly in front of Bellatrix.

"Winner," he said proudly.

"In your dreams," Bellatrix hissed and kicked him where it hurt most. Although he was in pain, he laughed at her while Bellatrix got up again. It took him only seconds to regain his spirit and he grabbed her neck, pushing her against the bricks of the chimney. Her throat was hot under his cold hands.

"Not so cheeky now, are we?" he breathed into her ear. He finally loosened the grip around her neck, but the rest of his body still pushed her against the wall. This was different. They had only fought with wands, never with their hands but Sirius was curious who would win now.

Their faces were so close now they almost touched and Sirius forced Bellatrix to look into his eyes. What he saw – the rising panic in her eyes when Bellatrix realized that escaping his grip wasn't at all easy – thrilled him, made him want to go further. Teasingly he pressed a kiss in her lips and received a kick in the stomach in return. Bellatrix, who had now struggled and freed herself caught her wand again and before Sirius could react, waves of pain shot through his body. He lost control of everything else and fell to the ground, his brain growing numb in agony. The pain was everywhere. The pain was him and the thought that Bellatrix was the cause of this feeling, that she was standing there, squealing with glee over his suffering made him want to hurt her even more. He knew she liked it, because somewhere in the corner of his mind he had started to enjoy it, too. More than that. It aroused him.

Eventually the pain died away, yet the feeling remained. When Sirius opened his eyes again, he spotted Bellatrix leaning against the wall, admiring her wand as though nothing had happened.

"Bitch!" he spat and darted off to her, catching both her wrists and pinning her to the wall once more. His knee was making his way up between her legs, causing Bellatrix to throw her head back and moan. Sirius let go of her wrist and his hand wandered down her neck, fiercely touching her breast and feeling over her ribs. She was so fragile, it seemed so easy to break her and breaking Bellatrix would mean winning every fight they had fought. But not tonight. Sirius' hand rested on her waist while hers had found its way under his shirt, digging her nails into the flesh of his back. He bent down, pressing a hard, violent kiss on her lips and even their tongues seemed to be fighting but Sirius didn't break off until he tasted blood.

He felt his trousers getting uncomfortably tight and Bellatrix, who seemed to have sensed it, opened the zipper to reveal his erection. Bellatrix quickly stripped off her slip and jumped up on Sirius, her legs winding around his hips while his stiff member thrust into her, making her scream with delight. Sirius closed his eyes, throwing his head back at the sensation of her tight cunt around his cock until suddenly a stinging pain shot through his shoulder where Bellatrix had dug in her teeth. Angrily he threw her back against the wall and thrust deeper, more violently into her. The pleasure was almost unbearable the closer he came to orgasm and he felt himself losing control. They both reached climax together, Bellatrix screamed loudly while Sirius only moaned with satisfaction, both his hands tearing on her skin. When he finally let go of her, Bellatrix stumbled backwards, panting. He felt her watching him and when at last he breathed normally again, he asked her.

"What are you staring at?"

"Nothing," Bellatrix chuckled, "I was just wondering who won this fight."

Sirius shrugged. "Equal, I'd say. As usual."

Bellatrix collected her underwear and wand and made herself ready to Disapparate.

"It can't always be like that," said Bellatrix, "One day one of us will kill the other. We're destined to do so."

With that she disappeared and Sirius knew that this woman would be the death of him. Or he would be the death of her. It didn't matter in the end because on this world was only space enough for one of their kind.