"Well, I... wouldn't be opposed to trying some more vials on you?" she stammered out. In all honesty, the way he looked at her, his huge, muscular body pressed against her back, arms tightening around her possessively, was a little scary. She just needed a bit of time to get her feelings in order before he fucked the life out of her... hopefully not literally.
As she was let down, she lead him to the kitchen where the vials were kept. She held up the Male vial to him, watching the blue liquid slosh around. "This is what I gave you to, y'know," she gestured at all of him. He attempted to grab it, but she moved out of the way.
"I would love to give you more of it," she started, though, in reality, she was a little terrified of what an extra few doses would do to him. "But I was thinking we could experiment and try mixing a few? Or take some different ones, I want to see what they do."
Greg nodded along, a little disappointed he wouldn't get another dose of Male anytime soon, but he loved his girlfriend and trusted that she was doing what was best for them. "Alright, so what are you going to give me?"
Mary bit her lip. "It's a surprise. Promise me you won't look?"
Begrudgingly, Greg closed his eyes and smiled. "Alright, go ahead."
Mary searched through the vials. While she didn't want to make her boyfriend more aggressive, there was still a part of her massively turned on by the huge, muscular body of her boyfriend, and she couldn't wait to get more of that. So, instead of warring between her heart and her mind, she let her body decide by plucking vials at random.
Into a cup went a dark green vial, a black vial, a splash of pastel blue and pink, and finally, a touch of orange. Against her better judgement, she added another dose of male to it as well, before handing the concoction to Greg. As he smelt it, Mary looked at what she'd actually given him, and her stomach sank.
Octopus, incubus, cock growth and invincibility, and finally, a touch of aggression to boot. "Wait, don't drink-"
But it was too late, Greg had finished his last drop, smacking his lips as he opened his eyes. "Honey? What's wrong?"
She backed away from him, and his eyes narrowed. Unfortunately for her, he stood in the only doorway out of the kitchen, and there was no way she could get past him. Which just left cowering in the corner as her only option.
Greg took a step towards her, concern in his eyes before he stopped short, convulsions wracking his body as the male vial kicked in. Mary could only watch in horror as he grew taller still, shooting up until his head grazed the ceiling, and then broke straight through. Each second of growth upward was counteracted by a surge of growth outward, as his muscled became larger and even denser. The raw power in each inch of his body was enough to release heat if he so flexed, creating explosive bursts of energy. Even without flexing, his body had heated significantly with veins the thickness of Mary's wrist covering his skin. His abdominal muscles surged forward creating a wall of muscle as his torso widened just to make room for his incredible bulk, each ab becoming larger than Mary's entire torso.
And across all of this dense, powerful muscle, hair began to grow in reams, covering his hulking 12-foot form in manly fur. As he hunched down just to fit inside the room, he looked like a bear, but he was far more dangerous.
Down below, his package grew longer still, snaking out towards Mary as it hardened, holding its colossal weight with the titanium muscle that bound it. It visibly pulsed with each beat of Greg's enormous heart, making it seem almost its own being as it quickly crossed the two-foot gap between the two, dropping huge globs of precum into Mary's lap as it reached her. Greg's pendulous balls were less the size of oranges, and more watermelons, bigger than Mary's head and audible churning with seed.
Greg held out a massive hand towards her. "See, that wasn't so bad, was it?" he tried, voice so deep and masculine he practically breathed dominance. In fact, with every word, his body created a musky cloud of pheromones, purpose-built to make those around him more pliable so the Alpha could have his way. "Cone here, Mary, please, don't be frightened of me."
Though there was some deep instinct to obey, Mary was simply frozen, watching as the next changes took place. The octopus vial. His legs began to twist, growing black and formless as they split into four tentacles apiece, sending him sprawling to the floor as the new nerves connected to his brain. Then, the 5-foot tentacles began to grow larger, longer, becoming 12 feet long, just as tall as he used to be, and thicker than tree trunks, the powerful, corded muscle filling them up until they were beasts in their own right. Mary pushed herself into the counter as they covered the entire floor with a black, fleshy carpet. Now in control, Greg coiled his new appendages under himself to stand, even taller than before, looming over Mary and blocking the light. "Come on Mary, this isn't that bad."
The next change came in the form of a blood-red pigment sweeping his skin. His masculine face grew more handsome, his eyes becoming pure black as he started to become hypnotically irresistible. He sniffed the air, turning his dark gaze to Mary. "I can smell your fear, darling. You didn't know what you were giving me, did you? But I promise I'm still your Greg. Just, bigger. Stronger. More powerful. The true alpha..."
His mind was trailing off as it was reshaped through the power of the vials, aggression taking over as his shoulders rolled back and he drew himself up to his full height, not caring what he smashed in the process. A tentacle snaked around Mary's body, immobilising her as he brought her up to his face. "Yess," he hissed, black eyes narrowing. "I can smell your fear. It's delectable, to see you squirm against me. But I can smell your lust too. It's only natural. You need me, you need to breed with the true Alpha!"
"That's not true!" Mary cried back.
He placed her down on the bench again, giving her the illusion of freedom. "Isn't it? Then why can I feel your longing, your desire to give yourself over to me?"
"You're lying!" Mary suddenly snatched a knife and dove at him. He didn't even move, laughing as the knife bounced harmlessly off him. With a flex of one of his pecs, he generated a shockwave that sent Mary flying, just by the pure explosion of muscle each twitch brought. He pinned her down with one hand, noticing how just one of his fingers was as large as her forearm.
"I gave you the option to do it the easy way. Now, we're doing it the hard way!" He accentuated the word hard with a thrust of his groin forward. He picked her up with ease, carrying her as he slithered to the living room, not caring what he destroyed in his path. Once he was in the bigger space, he lifted Mary with ease, before slamming her down on his cock. Half of it disappeared inside her ass immediately, leaving her crying out in pain as he continued to spear her, pounding into her over and over again until the whole two-foot shaft was buried balls deep inside her butt.
Tears ran down Mary's face. One of Greg's hands wrapped entirely around her waist, keeping her on the rigid fuckpole, while the other fondled her breast tugging them through her shirt. Inside her, she felt every twitch and pulse of the enormous cock as if it was her own. And then, she felt it grow inside her.
The first few inches came inside her, stretching her inside to their limits. The rest began to grow out of her, lifting her higher and higher as Greg's cock became a monstrous 3 feet long. She cried out in pain as she was forced down, the entire shaft inside her, then screamed as she felt something else prod up against her vagina. A look downstairs confirmed her worst fears.
'Cock Growth', the vial had said. Mary thought it would just grow the cock he already had. But no, right beside his original penis, another gargantuan shaft was budding, growing towards her vagina as if seeking it out. She squealed as it penetrated her outer lips, a sound which only spurred Greg on to fuck her even harder.
"You like that, bitch?" he growled as he thrust his hips into her hard, watching as his twin dicks pushed deeper and deeper into Mary. He brought a tentacle up to her mouth, smiling as the end became phallic. His muscles spasmed and burned as the extra 9 doses of testosterone raced through him, fueling his aggressive desire. Soon, Mary could do nothing but moan as all her holes were filled with Greg's huge, hard rods. Then, he got an idea.
Willing the end of another of his tentacles to constrict and become smaller, he pushed it into her ear, winding it through her all the way to her brain. Her eyes rolled back in her head as she was mindfucked by her Alpha boyfriend, as he changed her fear of him to devotion, her pain to pleasure.
Greg roared, the pressure building in all ten of his cocks, as thick cum burst from every one of them, firing shot after shot into her, and all over the floor. Soon, Mary's entire body, her ass, her stomach, her womb, and even her mind was filled with the thick, musky seed.
To Mary, her world went white, and then black, as she fell unconscious. Greg watched as his little mate collapsed, gently extracting her from his dripping and quickly softening cocks, and placed her swollen form on the couch. "You will be a good mate," he whispered. "Sleep, and when you wake, you will belong utterly to me."