Mark had always been fascinated with horses ever since he was a little boy. He praised their beauty and strength. He always wondered what it was like if he was a horse.
Without any hesitation, Mark pushed the button, which opened the box, grabbed the Horse Vial, which was filled with a dark red liquid, ran outside in his backyard, since horses were big and heavy, chugged down the entire liquid, and put it back in where is belonged.
"Ahhhh! That was refreshing!" Mark said.
Mark then started to change. His skin was being taken over by reddish fur, with occasional white spots on his limbs, butt, and back. His hands got bigger and his fingernails fell out, being replaced by thick solid hooves, which were enormous in size. His arms became muscular and bigger every passing second. His torso grew muscles too, revealing a very large and barrel-like gut.
His legs got bigger and stronger. His legs also grew large muscles that matches his new fore legs. His feet grew bigger as his toenails fell out, also being replaced by thick black solid hooves, also enormous in size.
He then felt a pain in his spine. A long tail pushed out and grew white hair all the way to the tip, which now hide his swollen horse anus. A long white mane started to grow on his back replacing the hair he used to have on his head.
His cock and balls, now covered in a black leathery skin, tripled in size, his balls become the size of grapefruits, and his cock becoming the size of a bottle rocket. Then it hid inside a dark sheath made from his former foreskin.
Mark felt a sharp pain in his skull as it was forced to push out into a horse muzzle, with his nose becoming a big horse snout. His teeth fell out, being replaced by big and square horse teeth. His tongue grew longer and heavier. His ears long and pointed. His eyes turned brownish and his pupils lost their humanity look.
Mark's body grew massively in size and mass as he got hundreds of pounds, until he was as big as a championship shire stud.
Mark's transformation was finally finished.
Mark looked down at his body, and was happy with what he saw. He had become a reddish mottled draft horse , complete with much power and strength.
"This is awesome!" Mark thought in joy because he had lost his capability to talk. He tried to say something but he only could make deep grunts.
Mark decided to test out his new strength. He started to trote in his back yard and some minutes later after he started to run. He can feel the power in each step he made, he felt so vigorous and strong.
After running for a while, he decided to run away from his back yard. So, Mark took a death breath in, ran towards his fence and using his strong hind legs he jumped over it.
"This is the coolest thing that has happened to me in my life! I've never felt this good before!" Mark thought to himself in joy during the instant he was in the air.
With that, Mark realized he could no longer live in his house, with him being too big. He could also no longer live around in his town, because he needed more space more freedom.
Mark ran towards the forest, looking for a new home, maybe he could find more horses or a farm where he could be taken care of.