I've been wanting to do this one for a while. I'd consider myself a Leorai shipper, and watching the fight between Leo and Karai in "The Deadly Venom" really gave me an itch. It was very emotionally beautiful I think, and I know Leo must've been hurting something awful, so I wanted to go a little deeper into that. And here it is. Disclaimer of course, these lovely characters (and the scene in which they've been placed in this case) never have and never will belong to me, but they are oh so fun to borrow.
Anyhow, with housekeeping aside, proceed, read, enjoy, and let me know what you think :)

*To any of you following Outspoken, I'm afraid writer's block has once again come to thwart my efforts. But I will claim my victory...one of these days.

"I don't feel so good."

Donnie's moan twisted up through the tunnel with an ominous echo that somehow got Leo to stop climbing.

The brick walls bubbled around him, stretched and shrank and swirled with colors he didn't know the sewers contained. He felt himself leaning back and tightened his grip on the rung of the ladder. He shook his head, pressing his tongue against the roof of his mouth to prevent the rise of bile in his throat.

"Me—neither." He closed his eyes, opened them again and continued climbing.

Donnie followed slowly.

They were soon walking along the subway tracks leading to the station. Donnie was dragging his feet. Leo thought for a moment that he should check over his shoulder and make sure his brother was still with him, but he was too nauseous to speak, let alone turn around. And if he stopped walking, he might not have it in him to get moving again.

He curled his fingers and they slipped against his sweaty palm. He held his hand in front of his face. It trembled before his nose. He let his hand fall back to his side. He blinked slowly, each step he made getting heavier and heavier by the second. His knees groaned at having to continue on. Would it hurt really—to just pause for a second?

"Leonardo and Donatello."

He snapped his head up at the voice.

"Sneaky coming from the sewers."

A violent shiver rippled through his skin, but he kept walking. His eyes stared at the ground, focusing in on his feet, watching as he carefully put one in front of the other and tried to block out her voice. She was close but he couldn't see her. He actually felt like he was imagining it, her voice, like it was in his head, bouncing back and forth between his ears. It gave him a headache, and yet, he didn't want her to stop talking.

"How are you feeling, turtles? Nauseous? Dizzy?"

"My brain is melting," Donnie said, whether to himself or in response Leo wasn't sure.

He looked over at Donnie, half intending to tell him not to speak. He couldn't hear Karai when Donnie spoke. But when Leo glanced at his brother, no words came out of him at first. We walked past him a couple of steps, staring all the while because Donnie's head was doing something funny.

He stopped. Blinked. And did a triple-take.

Yeah. That was a pineapple. A pineapple with wide egg-shaped eyes popping out of a purple mask, staring back at him as though surprised to see him. Yeah, the pineapple—the one sitting on top of Donnie's shoulders—was surprised to see Leo.

"Dude," Leo said, eye twitching. He stepped up closer to what had once been his brother and pointed with a shaky finger. "Why do you have a pineapple for a head?"

The mouth—of the pineapple … the pineapple—moved, and Donnie's voice came out of it.

I will never do drugs, Leo thought to himself.

"We've been poisoned."

Leo shook his head and ran, despite the burning ache in his limbs that protested with every strain possible. Keep going. Keep going, he told himself.

"We have to act fast," he said aloud at an attempt to goad Donnie on who was practically hyperventilating behind him.

"My venom is highly toxic in any form—even in water."

He stumbled a step but kept running. They were getting closer. Karai's voice wasn't in his head anymore. It was in front of him.

And then she was there, strolling down the middle of the tracks to meet them. Her red lips curled up into a smirk and she placed a hand on her hip, waiting for them to reach her. Leo narrowed his eyes on her, more to keep her in focus, to see her clearly and the way her scaly skin seemed to glow in the shadows of the tunnel.

"It seeps through the skin in seconds."

He slowed to a walk, breathing heavy, eyes glancing from Karai's right to her left at the Footbots coming up beside her.

Donnie groaned behind him, each breath he took sparse and wispy, his footsteps getting slower and slower until they finally stopped. There was a thud against the dirt packed ground and Leo finally looked back to see his brother lying facedown in the middle of the tracks.

And then it suddenly became real.

His stomach churned and he forced himself to look away. He couldn't turn his back on Karai. He was the only one left.

He drew his katana.

"It's over, Leo," Karai said, that smile still hidden in the very corner of her mouth. Her green eyes glistened with excitement and Leo could feel his face fall, could feel his body giving in.

He wasn't looking at the Karai he knew. But her face, in essence, was one he remembered, even if it was chalk white and covered in scales, even if she had glittering fangs and a snake-like tongue that passed quickly across her lips with a motion of hunger. Despite these things and the black laughing slits for pupils, there was still a secret tenderness to her presence that only Leo could see—that only he had ever seen. There was still the tiniest flicker of doubt in the way that she stood, a rigidness to her shoulders that she wasn't aware of. There was still an affectionate twitch to her nose when she said his name. She just didn't know.

His vision blurred and his body swayed. Everything tilted at an angle and the ground was suddenly catching his face. He didn't feel it.

"You and your friends are finished," Karai said, looming over him. "Finally, after all this time … Put them with the others, I want to admire my trophies."

Hands grabbed Leo's wrists and ankles, hands that were not hands he knew to be real. They flipped him over and his head lolled back. He didn't open his eyes but he knew the Footbots were carrying him somewhere. He'd seen Mikey, Casey, and Raph in the background, strung up by their limbs, unmoving, but it hadn't registered to him until this moment. They were going to do the same to him and Donnie and then leave them there until they dried out.

He sucked a breath in through his nose and furrowed his brow. "Rin," he whispered. "Pyo. Toh. Sha."

"The poison is slow. Within the hour you will all perish."

The Footbots stopped and dropped him. The bridge of his shell hit the ground and he elected to lie there as he was, flopped on his side. He concentrated all of his energy on the blood circulating through his veins, willing each separate chant to enter his bloodstream like an antibody.

"I don't even care about any of you," Karai continued, speaking as though to herself, though she addressed the tunnel as a whole. Almost as though she was looking for someone to listen to her, to hear her, like she had to have an audience to feel like she'd made an accomplishment, like she was doing what she needed to, filling a hole that had been eating away inside her, and yet … her voice was hollow in Leo's ears. She said she didn't care, but that couldn't be true.

"You're nothing more than a means to get to Splinter."

"Rin," Leo breathed. He would hear no more of this. "Pyo. Toh …"

With each articulation, he could feel his body inflating with strength. Air filled his lungs, his breathing became level, he tensed his muscles to make sure they would respond and opened his eyes with the final, "Sha," simultaneously slipping the hidden blade out from beneath his wrist guard.

"The rat will eventually come for you, and then I will have my revenge."

A surge of protective instinct reawakened his body when she said this. He lunged off the ground and spun a kick that took down two Footbots. The blade in his hand hurled out of his fingers and planted itself in the skull of a third Footbot, whose grip released the chain holding Donnie up in the air. His body fell and flattened the last Footbot.

Leo made a mental note to apologize to his brother for that later.

He stood on his feet now, but the effects of getting there hit him with a second's delay. His stomach yanked backward as though someone were pulling on it with a hook embedded in the flesh where his belly button might be. He gritted his teeth with a groan and placed a hand over his plastron, leaning forward with a bend to his knees to keep himself grounded. He squinted ahead of him.

Karai smiled. "Beating the poison. Impressive."

He grimaced and tried to breathe normally while she gazed upon him in his pain with no remorse. Beside him lay the body of one of his brothers while the other two hung above his head as though part of a crucifixion. But Karai smiled, and she taunted, and even despite that glimmer of doubt, she truly believed she was against them.

"Shredder," Leo said, breath rattling past his ribs, "used some kind of brain worm on you."

"Lies won't help you, Leo."

His heart skipped a beat and thumped a rhythm that could only be described as hurt. After all the time he'd spent, all the effort he'd put into convincing her that she could do better, be better than the Shredder and the horrible life he'd taught her, raised her in … and it was for nothing. She'd gone straight back to denial, straight back to a life of her own lies.

And yet, before her next words were spoken, she closed her eyes, tilted her head forward, as though to pay him her last respects, as though she was slightly sorry that she would soon dispose of him. But it only lasted a second.

"I'll just have to finish you myself."

She darted forward, rearing back her scaly arm and the snakehead flicking its tongue on the end until it shrank back into a bawled human fist.

He pulled a breath in through his nose and straightened himself to his full height, holding his arms in front of him at the ready, despite the nauseous turn of his stomach telling him he had no energy to fight—no will to fight. Nevertheless, he knew his odds and what it was that lay at stake and his eyes followed her movements carefully. He didn't tense his muscles until it was absolutely necessary, until she was right on top of him, leaping off of the adjacent platform and pitching quick, vigorous punches at his plastron. He deflected as many hits as possible, his feet automatically retreating backward.

He dodged a kick, pushed away her arm as it sliced toward his neck, and just missed another kick, nearly tripping backward in the process. His brain was still struggling to function properly. Every movement he made felt like it was moving through water, while her attacks were quick, sharp, and brutal. And yet, he still strained himself to talk her down as he blocked her attack.

"Karai, you have to fight it."

The snakes reappeared, extending from her shoulders and shooting toward him with matching hisses.

He'd learned long ago not to let the abnormal get the best of him. Life as a mutant turtle was nothing but abnormal. And yet, the snakes and their fangs still surprised him, especially seeing as he was not particularly used to seeing such a thing attached to Karai's torso.

He managed to evade the strike of the first snake but allowed his eyes to stare too long at the scales of the second as it shot past his neck and then curled around it. He choked as both serpents locked his arms by his sides and squeezed the air from this throat. Stars popped into his vision and he felt his feet leave the ground. He was heaved forward with a grunt and thrown halfway down the tunnel. His body arched through the air, suspended for a moment as though he could float there. But the weightless feeling of flight was broken by the impact of the ground hitting his shell and forcing the air out of his chest. His head smacked the compacted dirt, bringing a mirage of yet more stars, but they only increased in number as his body continued to skip across the floor until he found himself skirting against the tracks on his plastron and finally sliding to a stop.

It took a few struggling seconds for his lungs to work again and when they did, he breathed out a warbled moan.

He lay still, cheek pressed against the dirt, body pulsing with vibrations of pain, and all the while wondered what on earth would be evil enough to turn a good soul completely black. How do you bottle that? How do you feed it to an undeserving victim, a guinea pig, a teenage girl, and turn her into an instrument of malice? How does one live with himself for creating hate inside of his own adopted daughter? How could anyone strip someone they're supposed to love of their will and replace it with a hollow being of pure loathing? How was he, Leo, supposed to fight against the girl who had, without her own volition, forgotten how to love him?

He exhaled, blowing crumbs of dust across the ground, before slowly lifting his arm and gripping the metal rail next to his head. He picked his chin off the ground and pushed his body shakily to its feet.

But no sooner was he standing then the snakes shot out of the shadows and sank their teeth into each of his arms. He sucked in a breath at the shock of pain that pierced his skin. He could practically feel the venom seeping into his bloodstream, weaving liquid fire up his arms. The teeth pulled against his flesh, digging deeper into his muscles, and slingshot Karai forward. She came at him faster than he could comprehend and punted him in the plastron with both feet. The force sent him flying backward and ripped the snakes' fangs out of his biceps. His carapace hit a vertical beam. He choked. And his knees met the ground.

"Still feeling the effects?" Karai said, slowly closing the distance between them.

He panted into the dirt, beads of sweat dripping from his forehead and stamping the backs of his hands. His eyes glanced to the open wounds crying drops of dark red blood down his arm.

"You're weak, Leo."

He gritted his teeth, ignoring the sting that prickled in the corners of his eyes. A sour taste flooded the back of his tongue, bitterness, anger ... Weak? He manages to get back on his feet despite being infected by a deadly poison meant specifically to kill him, while she refuses to fight against a brain-sucking worm that's controlling her every action, forcing her to execute her own family, her friends, and yet he's the one that's weak?

"And you're done for!"

No, Karai. I don't think so.

He narrowed his eyes on her, drawing every bit of strength possible from the gleam of the scales plaguing her skin—the product of a cold heart, of selfishness, of blind vengeance and pride stuck on a girl who never deserved it.

He pushed himself to his feet one last time, leveled his shoulders and clasped his hands together.

"Rin. Pyo. Toh. Sha."

He glared at his hands, concentrating on each mudra and its precise execution, extending, folding, and intertwining his fingers.

"Kai. Jin. Retsu. Zai. Zen."

His veins buzzed with energy. His lungs pulled in healthy, invigorating air. His stance solidified. And his mind reawakened. The details of every grimy brick along the walls and smudge of dust and dirt on the tracks became sharp. His nose picked up scents it had neglected before—blood, rust, damp, sour air, and ginger. His ears collected every noise, including the pace of Karai's breathing.

"Rin. Pyo. Toh. Sha … Rin. Pyo. Toh—Kai. Jin. Retsu. Zai. Zen!"

A glow of white spread from the tips of his fingers and outlined his skin, running up to his wrists.

"What are you doing?" Karai said, eyes wide. "What is this?"

He pressed his palms against his plastron and breathed in, allowing his eyes to close. The glow spread outward from his hands and flushed its way through his body, washed the venom from his blood. Warmth seeped into his muscles, firming them up, giving them power that pulsated through his limbs and down the spine of his shell. His next breath weaved throughout his lungs like water reviving his body. Only when he felt the tingle of energy in every inch of his being did he let his hands slide from his plastron and rest by his sides.

Karai moved, her feet lightly sprinting across the tracks as she darted straight for him, voice giving out a cry of panicked anger.

He opened his eyes, watched hers glitter a venomous green as they flashed on him with that very same hatred that did not belong to her. She flung a serpent arm at him and he turned his body away. As it shot past him, he threw up a sturdy block and knocked her arm away.

"Rin!"

The snake fell limp upon the ground with a shriek, paralyzed. Karai growled, glare furious. She hurled the second snake at him. He twisted away and struck it too with his forearm.

"Pyo!"

The second snake fell. Karai bared her teeth and grunted a shout as she propelled herself into a flip and brought her heel toward his face. He met it with his fist and took the impact with an unmoving intensity that rippled up her leg.

"Toh!"

She landed shakily on her feet and he darted forward to catch her midriff with his fist before she could fall.

For a brief, suspended moment, he could feel her breath dragging into her stomach with a tremble. Her pulse hugged his knuckles pleadingly, and her muscles involuntarily let down their guard, relaxed, became soft and vulnerable. And he held her, willing every ounce of strength and power he had to funnel into his fist and connect to her somehow—to the Karai that he knew, that he missed, that he loved. In that moment, he could feel that Karai struggling to break out of a cloud of darkness, and his arm gave the slightest of trembles, desperate to reach out to her and pull her out of it. But she would not reach back, and this fueled him with hurt, with desperation, and he let that fill his body and pour out into his hand as he pushed with all his might and screamed a final, "Sha!"

And then she was gone, tumbling and rolling across the tracks until her back hit a beam and the force snatched her breath away. Her eyes, for a moment, stared wide with surprise into the distance before they slid close as her body sank to the ground and didn't move.

He remained standing, staring at her from across the tracks, fists still curled and now shaking by his sides as his chest heaved.

He knew it hadn't worked, and yet he'd wanted it badly enough to still hope that maybe it did somehow. But the longer she remained motionless the more his hopes were drained. He was still staring at the girl who had been stolen from him and made into something else, something inhuman, something that would forever be incapable of love, of understanding, of forgiveness.

Something wet rolled down his cheek and he wiped it away only for it to be followed by another, and then another. He grimaced and rubbed his palms furiously against his eyes, but the spring of tears did not subside and soon he found himself on his knees.

He threw his fists against the ground and held his breath, staring through the blur as though it might go away if he glowered hard enough, but it only worsened, thickened, and he finally found himself choking on a sob as his expression softened. He leaned forward, buried his face in the dirt, and cried.