Katherine looked down at a vial with a thick, blue liquid. The heady smell arising from it hit her new, sensitive nostrils immediately. It was like musk, or maybe even pure testosterone, the sort of scent that made her pussy clench from need. But, she thought, if she could stave off her excitement long enough for the vial to work, she might just have the best masturbation session of her life.
Groaning, she took the vial and swallowed it down in one gulp. Then, because she wanted this to be as hot as possible, she waited for it to refill and downed another dose. Her hand trembled as it came up to her muzzle, the first vial already kicking in. She just managed to put the vial back into its place as the transformation really took hold.
Katherine gripped onto the sink as her muscles quivered, then ballooned outward. She clenched her teeth as her already impressive physique improved until she was a huge hunk of immovable musculature, each bicep bigger than a human's torso. Her grip faltered as her back was next to grow, instinctively arching backward and clenching her fists as her spine creaked and groaned. Several pops and snaps sounded out as her whole body grew bigger. From 7 feet she soon found herself at 7 and a half, then 8. Abs popped out large and defined as the bricks in the walls of the now almost claustrophobic house. Her equine ears brushed the ceiling.
But that wasn't the only change that happened. Katherine felt her face begin to ache as her jaw creaked. It became heavy and strong, and her whole body broadened once again as she began to hunch in the kitchen. 8’5, 9’ she became, though, as the vial pumped through her veins, she found that ‘she/her’ wasn't quite the way to describe it. Killian emerged from the mind of Katherine, a man, a stallion, testosterone flooding through his system.
Killian thudded to the ground, groaning, legs stretching out long and pumped full of muscle, thick as tree trunks. His vagina, which had until now stayed throbbing and hot and aching for pleasure, was now beginning to change. His ovaries popped out from inside his body, now two large testicles the size of melons wrapped in a leathery sack that hung to his knees. But the real meat was the spire that telescoped out from his groin. Thick and uncut, a musky smell began to arise from it. It quickly surpassed a foot in length, rigid as a steel rod. Killian moaned as it stopped at a whopping 2 feet, thicker than a can and dripping in precum.
A stud, he thought to himself as his huge hands found themselves on his even larger cock. That's what I am. A stud. His hands slipped back and forth. It was very different from the pleasure he’d experienced as a woman, and his size hadn't decreased the sensitivity of his dick one bit. His nerve endings were alight with this strange, new sensation, throwing his muzzle back as he whinnied in sheer delight at the pleasure it brought him. Made for fucking, for breeding, he thought as he thrust his hips up into his desperate, grabbing hands. Inexperienced, Killian was on the verge of orgasm in seconds. He didn't have the willpower to hold back.
The stallion roared in delight as his cock unloaded a deluge of cum with enough force that it hit the ceiling above. Several more shots followed, though none quite as powerful as the first, so it came down as a musky white rain, splattering across his dark fur. Once his huge body had been adorned in a galaxy of cum drops, Killian finally felt the pressure in his loins ease. His cock softened in his hands, and he laid back against the kitchen floor, collecting his breath after his first mind-blowing orgasm in a male body. God, he was looking forward to more of that.
There was a clatter from the living room. Killian lifted his head. “Mom?” A voice called out. “Where are you?”