An Avenger's Guardian

"You know I don't think she is respecting us sister mine," Nebula stated teasingly, sliding behind the green woman as she spoke. Still holding the human down, Gamora was forced to lean over the frightened redhead as her sister pressed into her back.

"Perhaps the Terran just needs further incentive..."

Natasha's eyes widened in sudden fear as she felt something else between her cheeks, colliding with the phallus already buried there:

"-Wait- Unnnghhh!! I said what you wanted -UhhhhhHHH!"

Gamora stared, shocked, into Natasha's eyes, watching as the human was pushed too far, feeling her sister's hands find leverage around her own supple waist.

Nebula smiled and pressed her dildo against Natasha's already widely stretched ass hole. Rolling her hips to find a decent angle, she slowly but firmly pushed forwards, violating The Black Widow's butt with alien strength. Feeling resistance, she wriggled her hips forward, her shaft brushing against Gamora's nethers. Baring her teeth, the green woman swallowed the pleasurable sensation of this unwanted massage, feeling terrible for the stuffed human.

Feeling the second dildo's head driving inside her, Natasha screamed wantonly, the phalluses grinding together, both stretching the redhead's back passage far beyond its capacity. Grinning madly, Nebula held the two other women as she put them both in their place.

While shoving a dildo up Natasha Romanoff's ass was unnatural, Nebula was in no doubt the redhead had been stuffed before. Two dildos however was definitely a violation, one that finally overcame Natasha, causing her to cry out desperately:

"You're my Masters! You own me, this body -AHHHH!"

Gamora, feeling helpless, watched on in horrified fascination as her sister split the human's asshole in two, angry at herself for enjoying the rich stimulation of that cold shaft gliding against her pussy lips as she failed to guard the redhead. Watching Natasha's face contort between agonising pain and delirious pleasure, she saw her lip tremble, her eyelashes flutter and her mouth twitch. Then suddenly she felt Nebula's crotch press against her behind. Under such force, Gamora crumpled forward, the stronger blue woman not stopping until both of their cocks were deep in the human's asshole.

Twisting her hips repeatedly, Nebula worked both dildo's into Natasha, shunting forward to bury them both inside the redhead.

Gasping for breath, Natasha flexed in place helplessly, back arching off the pool's rim to accommodate everything her insides were encountering. Strong legs flexing, she wrapped them around Gamora's neck, the redhead almost strangling the brunette as they tensed together, both feeling betrayed.

Flailing, Natasha grasped her sore belly, cramps shooting up from her rectum as she struggled to adjust to two huge cocks. Feeling a bulge in her abdomen, Natasha realised these aliens had now gone deeper than ever before, the redhead screaming in horrified ecstasy.

Running a hand through wet red hair, Gamora tried to calm the human down, even as her sister slid the hot shaft deeper still, twisting the rod like a knife in their collective backs.

Natasha screamed, her sensuous voice breaking into a groan as she felt the hilts of the two cocks stretch open her ass cheeks impossibly wide. The redhead swallowed hard, her eyes misting over in shock: the entire lengths of these shafts now inside her warped behind.

And then Nebula pulled herself and Gamora back and Natasha screamed yet again, her body jerking uncontrollably as the blue woman began to pump them both in and out of her anus, unable to comprehend the dark sparks of pleasure that came with each thrust; even as her body was destroyed.

What was happening to her? This utter violation of her being? Even as her stomach lurched and churned, two shafts pummeling her colon, Natasha felt her pussy burn with deep, impossible lust.

Working against Gamora's usually controlled balance, Nebula began to drive the two shafts deeper and deeper with un-tempered ferocity, waves of liquid spilling around their twisted bodies as she stimulated her sister and double sodomised Natasha with reckless abandon.

Clutching her belly, Natasha's chest bounced with every thrust. No longer holding onto the poolside Natasha slid deeper into the dark, rippling oil, Gamora gripping the rim instead to hold them both up as they almost sank.

"You want this don't you Earthling?" Nebula spat, enjoying watching the human sink into the ooze around them even as she continued to pound the redhead's behind:

"Is this -Ah Not your natural state?? Its the-ugh!-unspoken truth of Humanity! Ugh -you crave subjugation!!"

Thighs loosening around Gamora's waist, Natasha's eyes rolled as her head lulled backward, tears dripping into the liquid around her head. It took all her strength just to stay conscious.

Squeezed between her supposed saviour and utter damnation, Natasha felt contorted and ecstatic even as her bowel expanded painfully, the pool inundating her depths.

"This is how you take them sister mine," Nebula whispered into a green ear:

"With nothing held back!"

Natasha cried out, eyes blurring as she came hard, losing control of her bodily functions. Tensing, her insides burned with pain and pleasure, the liquid swirling around her bloated belly. Tangled beneath the two aliens, more bubbles broke the rippling surface.

Feeling Natasha's cheeks flex and stretch, Gamora grimaced as the redhead burst, spraying her with vacated liquid and cream.

Gamora's guilt threatened to consume her, holding the human's pale face as she endured this unimaginable penetration; she had wanted to spare her this. Instead she had been helping.

Nebula made sure to roll her hips in imaginative ways, gyrating like a stripper, the most sadistic part of her grinning wickedly as Natasha cried, the two cocks rearranging her bowels. Meanwhile Gamora refused to do the same thing; even staying still while her dildo skewered the human. The two sisters did however, share a knowing look as they stretched Natasha's ruined back passage. Even through the most extreme acts they were still together; opposed, but never truly apart.

Natasha used to fight against making a sound, really make her lovers earn the right to make her moan with pleasure. But she never stood a chance here, not when she was getting double ass fucked by a pair of aliens. Then again, getting two dildos shoved up her ass at the same time was extreme even in spite of tht. And so what else could she do in response to this invasion other than grunt, whine and snort.

This was it; she had gone to far. Sex was her ace in the hole, Natasha's get out of jail free card: Until now.

It only got worse for Natasha when Nebula finally started pumping her hips back and forth with a regular rhythm, forcing those two dildos to slide almost out of her back hole before being pushed back inside again, the gap between them pumping fresh liquid around her bloated insides. And instead of being disgusted, Natasha actually felt pleasure, even from this obscene anal assault. How had she come this far?? What happened to those nights in the barn?! Natasha had thought she had known kinky sex; She had been so wrong.

Staring into Gamora's eyes throughout her domination, the two beings finally came to understand the reason for their connection; that deep, dark, underlying submission they both shared, to powers they both had tried to ignore. Greater than Maria Hill. Greater even than Nebula. Seeing that apology in Gamora's eyes, Natasha came to realise the real threat they both faced. Unfortunately for the redhead, at that moment it was not her face she was worried about. Could she give Nebula what she wanted if it teared her apart?

Meanwhile, the blue alien found it increasingly frustrating that Gamora wasn't subjugating the Terran too. No, her lazy sister was just sitting there and letting Nebula do all the work! Couldn't Gamora tell she was just trying to share this moment of joyous victory with her?? Obviously her softer sister was going for a slow butt pumping, to try and get the girl's back door and passage used to the idea of being double penetrated, but now her bowels had loosened up the Terran clearly craved the type of rectum wrecking only these two women could give her. So why was Gamora so still!?

Natasha looked between the two aliens. Seeing those dark eyes glare at the back of Gamora's head, Natasha realised what she had to do. Soon she became desperate enough to choke out a plea:

"Mmmmmmmmmm, ungh, Unnngh! Fuck! Fuck me, fuck me harder! Aaaaaaaaaaahhhhhhhhhh Gamora, fuck my ass please, I need it fucked! Mmmmmmmmmmmmm, I need it pounded hard and deep -AHhh Uhhh! oooooooooooh Gamora please, ohhhhhhhhhhhhhh, please, wreck my ass! Fucking destroy it! Destroy my big fat human butt! Both of you ooooooooooohhhhhhhhhhhh Gawwwwwwwwwwwwd, please, please, do what she wants! Please, please, please I need it, I need you! Unngh! OH GOD! Oh God, oh God, oooooooooooooohhhhhhhhhhhhh!"

Natasha came hard, her eyes rolling as her words failed her once more. Looking over her shoulder at Nebula, Gamora saw the glare she'd wanted to ignore.

Nebula growled back at her sister:

"Fuck her Gamora! Fuck her hard! Use your cock to fuck this slut's asshole! Show her the ruination Thanos will reap on her world! Destroy Natasha Romanoff's big, fat ass and make the 'mighty' Black Widow beg for our mercy!!"

Hearing her sister's taunts, Gamora looked down at the heaving face of the mangled redhead; slack jawed, wide mystified eyes, tangled wet hair, breasts bouncing with every painful stroke, covered in hickeys and scratches. This human was stretched beyond capacity. If she joined in now, they would destroy her. If she didn't, Nebula would ensure they both faced the consequences...

Leaning down, Gamora pressed her green lips to the exhausted redhead's, just as the human came again, convulsing helplessly. Swallowing the woman's tortured shriek, at that moment the alien made up her mind:

"No."

Nebula paused mid-stroke, making the stricken redhead whimper:

"What?!"

"I said, No."

"This is the will of Thanos, the Dark Lord! The Mad Titan-"

"Noooo!" Gamora yelled defiantly.

Suddenly shoving backward, Gamora shunted her sister into the pool. Dildo coming free with a wet slurp, the blue alien crashed into the colourful oil, splashing the other two women.

Natasha gasped in relief, her gaping hole releasing the liquid that had been churning through her gut. Expelling the alien fluid, Natasha cried out, still holding Gamora in her loose grip.

Bubbles bursting to the surface around the two women once more, Natasha came once more, this time out of sheer relief as her Guardian cradled her.

Rising demonically from the liquid behind Gamora, Nebula raged, spitting oil as she returned:

"Really sister mine?! You would defy his will??"

"Yes," Gamora replied simply, not bothering to turn to the warrior woman as she held the fledgling babe.

"You know he will destroy you for this?!"

"Not if you don't tell him," Gamora hissed, stroking red hair as the human lapsed into merciful unconsciousness.

"And why would I do that?!" Nebula spat.

Looking down on the sleeping human, holding her against the rim of the pool, Gamora shook her head wearily. Flexing her hips, the alien woman arched her back:

Nebula watched in amazement as her sister's dripping behind rose from the oil, perfect green apples perfectly poised before her waiting gaze. Observing the tattoo on her left cheek, Nebula bit her lip; the mark of the Mad-Titan shimmering in the dim light.

Finally twisting to face the blue alien, Gamora spoke clearly:

"Then take your satisfaction Nebula."

Genuinely taken aback, Nebula's eyes travel over the subject of her desire. Imperceptible dark orbs rolling over this sumptuous offering, it took her less than a second to make up her mind.

The warrior woman smiled darkly.

Wafting up behind her sister Nebula groped delectable green flesh; tearing apart those cheeks to exposed the hidden starfish in-between.

Turning back to Natasha, Gamora exhaled determinedly. Was this her redemption? Or her fall from grace??

Reaching for her dildo, Nebula considered it briefly, before grinning cruelly at her sister's glorious behind.

Plucking the metal phallus free of her groin, the blue alien threw it aside.

Hearing the clang of her shape-shifting dildo rolling away, Gamora bared her teeth, bracing herself for what she knew this must mean.

Raising her metal arm, Nebula cracked her hard, unyielding knuckles, oil rolling of her mechanical limb and dripping back into the pool as she studied her prize.

With no further patience, the blue woman extended two metal digits: burying them in her sister's asshole.

Gamora howled, eyes wide as she was cruelly invaded, fingers prying open her taught sphincter to get at her insides.

Feeling the burn, she swallowed her pride as Nebula pulled her ass cheeks apart, twirling and flexing her fingers inside her anal canal. Her pressure and strength was unbearable, every shove brushing her own nethers against Natasha's naked core.

For all her humiliation, Gamora could live with this. For once she was protecting another, instead of destroying them. No fighting, no killing, no cruelty. This was compassionate. Unfortunately, the same could not be said of Nebula's actions.

Soon another metal finger joined the others, working Gamora's asshole insistently as she pried open her sphincters, determined to reach inside. Holding still, the green woman tried to relax, taking deep shuddering breaths as Nebula's other hand slipped digits into her butthole. Sliding against her inner walls Gamora felt the hypnotic oil trickle into her open anus. Three fingers, four, five fingers, some flesh, some cybernetic. Breathing hard, the alien held her tongue as she was brutally invaded.

Stretching her sister open, Nebula peered into the gap she had created, smiling widely as she glared into Gamora's pink insides. Instead of slithering away like she had suspected, her sister seemed almost proud, her back perfectly arched, pressing against her fingers as if inviting Nebula in. The blue woman smirked; Gamora always was a martyr.

"You are a natural submissive sister mine," Nebula laughed cruelly: "Who do you think you are?! Some kind of Guardian to this pathetic creature?!?"

Sliding 4 fingers into Gamora's bottom, the alien hissed, shifting uncomfortably as the cybernetic hand wriggled inside her. Dropping her head against Natasha's full chest, the green woman suppressed a whimper, even as she pushed her behind back against her sister's might.

Roughly sliding her pointed fingers deep into Gamora's open rectum, Nebula felt her sister's insides squeeze her unyielding metal limb, as if attempting to eject her. Grinning, Nebula curled her fingers, stretching her sister's vulnerable flesh. Then, folding her thumb into the palm of her hand she began to gently push her whole fist between those fleshy green cheeks.

"SLURP!" her hand, aided by the pool, glided right past Gamora's burning sphincter and inside her stretched rectum.

Feeling Nebula's wrist meet her backdoor, the green alien flinched, shunted forward as she was controlled like a puppet.

Clenching Natasha's breast desperately, the redhead awoke as Gamora jolted forward, hazy eyes meeting the bulging pupils of the alien woman at that very moment of total sacrifice and submission.

"AHHHHHHHHHHHHHHH!" Gamora yelled, her body contorting and flexing with this strange weight buried in her forbidden hole. Unable to buck free, the green woman struggled, teeth bared in reaction to the intense pressure in her abdomen. At the same time she slid against Natasha, their breasts, their nethers mashing together to provide some measure of bizarre comfort. To her shame, Gamora felt an orgasm building.

Nebula cackled triumphantly as Gamora's anus contracted and convulsed around her metal wrist, standing tall above the two women she had subjugated. Reaching under Gamora, she felt the pulsating heat of her swollen core. Rubbing and pinching that familiar clit, she soon brought her flexing green sister to orgasm:

"Arrrgh, Arrrghhhh, AARRRRGGHHHHH!!" Gamora she came, the tremendous ecstasy rocking her emotionally and physically. Instinctively closing her powerful legs, she clinched her large round buttocks, trapping Nebula's wrist as her whole body tightened.

Nebula could feel Gamora's anus contracting and quivering from the waves of her orgasm, practically mounting her sister as she came. Beaming she roughly pulled her fist from the velvety warm depths of the green woman's bottom.

"SLURP!" Coming free with a squelch, the blue woman laughed as Gamora's anus sucked at her wrist, before gazing at the glorious sight of her sister's gaping crater.

Gasping, Gamora felt the cold clenched fist puncture her yet again, mouth wide as Nebula pummeled her bowels with her cybernetic hand.

Twisting her arm left and right, Nebula giggled with satisfaction as her sister flexed to accommodate her every move with no resistance at all. Beginning to piston her metal arm in and out, she watch with fascination as Gamora's body gradually took more and more of her, green ass cheeks now inches apart.

Watching her wrist disappear from sight once more, Nebula cackled with joy:

"How can you bare this Gamora?! Your slutty ass taking my arm as if it were made for fisting??!

Growling hollowly, Gamora rolled her hips, trying not to give Nebula the satisfaction of her suffering, even as her belly swelled under every thrust, the pressure of such pain and pleasure almost unbearable.

"You thought you were so righteous!" Nebula rallied, thrusting her fist harder and deeper into her sister's ass:

"Bu this is the truth, sister mine! You're a dirty, Zen Whoberi slut!!"

Nebula slapped her sister's muscular bottom hard:

"Take it bitch! Take my fist up your hungry green ass!"

Anger overtaking her painful pleasure, Gamora thrust back against Nebula's arm, wincing as cold metal rearranged her vulnerable bowels. Humping her sister's arm, soon the blue alien was achieving even greater depths.

With every slice of Nebula's cybernetic arm, there was a pronounced squelch, the pool's oil lubricating what should have been a much slower, softer pounding. Shifting her limb back and forth, the blue woman had her sister just where she wanted her, as if possessed by the triumphant augmented alien.

Knowing how nasty this encounter had become, Gamora focused on the dazed human below her, praying she had made the right choice, even as she felt another orgasm well cruelly inside of her.

Opening and closing her fist Nebula twisted her wrist, reaching deeper and deeper inside her flailing sister. Knowing fisting was considered depraved throughout the galaxy, Nebula grinned in deep satisfaction. How many times had she been altered by the will of a much greater being, only for little miss perfect to win the day? If Nebula had been transformed on the outside, she would transform Gamora on the inside.

Feeling that cruel hand pressing into her intestine, Gamora convulsed, green breasts shuddering like jelly, black and pink hair flying as she fell forward onto her human counterpart.

Their faces millimeters apart, Gamorra whispered desperately:

"Whatever nightmares your future holds -ahhh! Remember those are dreams -mmm, compared to what's behind me!"

Nodding, Natasha held the green woman. Resting her head on the human's chest once more, Gamorra took solace in this strange embrace, even as her ass was ruthlessly pummeled into submission.

Nebula cocked her head, staring down at her defeated sibling; full breasts flattened against the Terran's, her behind perched up as high as it would go, fresh green ass cheeks glistening with the pools oils. Looking down at the metal arm embedded in that once proud rump, the blue woman paused. Deep in her cybernetic mind, she felt her suppressed jealously twinge, her eyes narrowing, her expression darkening: