As Brian discovered he had gained a horse's tail, the room lurched and spun around him a moment, and it became darker and far more aromatic. He blinked as his eyes adjusted, automatically thrusting once more, only to have his belly hit the base of a long-haired tail. He gasped, pulling back and thrusting again as he realized he was mounting a large, dark-haired mare in a stall!
There was a chuckle from the side, and he turned his head to see Llandros, the wizard, smiling from the next stall over as he watched. "Since you did not seem to be enjoying pleasuring me, I decided to give you a companion more suited to your equipment. Which, I think you'll be happy to know, is becoming even more suited to your new companion!"
Brian could only grunt in reply as he drove in deep, the thrust incredibly long and sensations very intense. It took real effort to plunge into the slick black lips of the mare - there was a lot of him to pull in and out. The mare squeezed internally and whinnied, and Brian gasped and made a strange strangled cry that almost sounded like a neigh. It was hard to think of anything other than the mating, but he saw that his arms were longer and thicker, and the skin was covered with dark hair.
"You're... turning.. me ...into... horse!" He gasped out the words with great effort.
Llandros shook his head cheerfully. "Nope! You are turning yourself into a horse. A very handsome Percheron, if the spell on the mare holds true. The longer you mate with her, the more horselike you become. And you won't be able to eject the massive load you have built up in those huge black balls until you are one hundred percent stallion."
It was true, Brian realized. Two more thrusts and the dark hair on his arms had thickened into actual black fur, and his fingers were swollen and going numb. "No! Don't... want... be... horse!" Each word was shouted out with a voice that got more cracked and raspy.
"All you have to do is pull out before you cum." Llandros grinned. "Just slide off her back, stop the mating before it's finished. I won't do anything to stop you."
Stop. Mating. Brian had already thrust again as he seized on those two words. All he had.... to do was to ... pull out. And then push back in. NO! The need to mate was instinctual now, stallion's desires building to reinforce his intense pleasure, and control was almost gone. He felt so big now, still grunting and sweating with effort, but with mass that pushed the ever-expanding cock deeper. Brian was aware of his shaft in a way he had never felt his human sexual parts. It was fully equine now, a flat, flared head on a thick, veined shaft as long as his elven legs had been. Not that his legs were those slender matchsticks now - he could feel the powerful muscles and heavy hooves, the flowing tail that twitched back and forth over his furry rump.
But he could also feel his head changing. There was an oddly pleasant sensation of pressure as his skull flattened, the dome sinking like a deflating balloon even as his eyes drifted apart. Brian's brain was altering to fit its new quarters, causing some mild confusion and and a growing thickness of thought. He was starting to think differently, his ability to use abstracts and imagination dwindling as intelligence dropped.
And yet Brian kept thrusting in, fully aware that he was at least three-quarters horse and heading for a spectacular finish. Could he stop now? Did he really want to? The intense pleasure and base instinctual need was satisfying in way he had never experienced before, and the encroaching equine mentality was far simpler and easier. Living for the moment, the now, with no real concepts of death, danger, worrying about the future.
His thrusts were slowing now as he built to release. The mare shuddered and whinnied underneath him, and he shuddered and whinnied on top. Nose and mouth were protruding out, and his arms were more forelegs ending in hard, three-fingered hands. Pressure. Need. Pleasure. Need. Sex was almost all-consuming now, and Brian realized he had reached the final decision point. He could try to throw himself back, disengage from the mare and stop the total transformation that was just a few thrusts away. Or he could give in and complete both the mating and his transformation into a Percheron stallion. His biggest fear was not the animal body, but the possibility of losing himself. So far he was still Brian in his head, even with the shifts of comprehension. He suddenly understood Mike's fascination with going from centaur to horse. While the body was amazing, the simple focus of the equine mind was hypnotic.
He felt fingers close up, meging into massive hooves, and the joints in his arms began the final migration to work as true forelegs. They were done in two more powerful, grunting thrusts, and his face drifted outward into a black muzzle with the next. He could see Llandros smiling in satisfaction now, Brian's equine eyes providing a nearly 360-dgree view that was somewhat grainy and lacked much color. The wizard seemed confident that Brian was done.
Maybe he was. Brian felt the pressure in his loins, the throbbing of his shaft. To pull out now would short circuit the primal instinctive need his stallion's mind was almost totally focused on. In fact, he was amazed he could still think at all, much less struggle against the tidal wave of passion.
Brian drove in deep, shuddering and whinnying, and started to draw back. This was it. One more thrust and he would complete the act. He had to either throw himself off or accept the consequences of total transformation into a beast of burden.