.

Warning: This story contains two endings. A mild version and a more aggressive ending. 

Dark clouds rolled through the sky as a sleepy bat-bun yawned. The steady rocking of the boat lulled the hybrid to sleep. Rubbing his eyes he looked out over the bow, on the horizon what had been a speck a few days ago now was an island, complete with a large castle perched on the side of a high cliff. The bat-bun’s short tail wagged at the sight.

“A real freaking mad scientist castle,” he bubbled to himself, still not quite sure how he won a contest to cosplay at a real castle when he couldn’t even remember signing up. The boat lurched as it slid alongside the old rotting dock. A large carriage with a large black horse waited at the end of the dock as the honored guest disembarked. Seeing nobody around the bat-bun picked up his luggage and climbed into the carriage.

“Hello driver?” He tried to peek past the curtain dividing the cab and driver’s section but was thrown back as the carriage lurched forward. Pressed against the seat the bat watched as the the coastline shifted into rocky mountains. The carriage rattled and rocked as it barreled up the steep and narrow road till it stopped in front of the castle the bat had seen from the boat.

The door to the carriage popped open on its own with a loud squeal. The occupant shivered as he stepped out of the carriage onto hard stone. Alone the bat turned to collect his belongings. “What outfit should I wear?” He muttered as he mentally envisioned himself in his lab assistant cosplay, complete with a hunchback and tattered lab coat. “Nah, maybe my lab creature outfit would be better.” The bat commented as his sensitive ears alerted to the sound of a door creaking open. 

“Who’s there? Hello?” The bat called out, as he walked towards the sound, his missing bags forgotten for the moment. Out of the corner of his eye he caught a glimpse of a shadowy figure lurking through a dimly lit passage. “Hey!! Wait up!!” The bat dashed after the figure, through a door he hadn’t noticed before, and into a large stone chamber lit by dim bulbs.

The room hummed and crackled with electricity as the loosely wired lights flickered. The bat could see the shape of two figures between the flashes. As he tried to shield his eyes with his thin wing membrane the bat shuffled towards the figures. Two large horses came into focus as he approached. Both equines wore long white lab coats that hung open. One was a large rust colored mare, her breasts spilled out of the coat as she worked on some unseen project. Next to her was an even larger stallion, the color of his fur reminded the bat of the night sky, pitch black with bright specks of white. Slowly he lowered his wing, his eyes finally adjusted to the dim lighting.

“Shush!!!” The large stallion hushed the bat hybrid with a huge gloved covered hand before the bat could even open his muzzle. The stallion’s hand completely covered the bat’s face as the horse turned. The large male pulled his hand away revealing to the small guest a huge black member with a massive sack dangling below. Like the mare the stallion wore his lab coat wide open.

“Um?” The bat-bun stood there lost as he stared at the naked equines as the mare poured something from a glass beaker into a small vial. The mare looked down at the smaller male, her coat flung open just like the stallion. The bat-bun swallowed surrounded by the two equines, This is awesome, so realistic!!, the bat thought to himself as the mare turned, her large equine member dancing in front of the bat.

“OHHHH, Our guest is here!!! Why didn’t someone say anything sooner?”

“Well, I just picked him up from the docks. You know how rough it is to pull that carriage all the way up here,” The male responded, his large hands up in the air. “And, didn’t want to interrupt your experiment.”

“Ahh, well welcome to the castle, I’m Dr. Thistle and this my brother Dr. Thorn.”

“I’m Butterscotch,” The bat hybrid squeaked as he looked around. Now that he could see the room was filled with various equipment, some that buzzed and hummed with raw electrical current while other machines simply held ominous switches and levers.

“That is a cute name,” Dr. Thistle chuckled as she pushed a cork into the vial to prevent any of the fluid from accidently leaking. “So, we can give you a tour or should we get right into the experiment?” 

“Ohh, let's do an experiment please. The boat ride was so long I just want to have some fun,” Butterscotch jumped exuding excitement wondering what his role would be. Dr. Thistle looked over at her brother and both equines nodded to each other.

“Before we start we need to get your vitals and measurements.” Dr. Thorn explained as he gestured to a chair. “Please strip and sit.” The large stallion guided Butterscotch towards the chair as Dr. Thistle pulled a pen and clipboard out of a pocket. 

“Oh ok,” Butterscotch’s cheeks turned pink as he undressed, laying his clothes in a pile next to the chair. His greyish-blue fur did little to hide his nudity as both scientists ran their hands over the subjects body. 

“Light frame, hollow bones, wing membrane,” The stallion called out Butterscotch’s traits as his partner wrote them on a sheet. “Male, Neutered” The batbun blushed as the stallion’s fingers brushed the empty spot under his sheath. The equine’s thick digit pressed between Butterscotch’s rear making the small male moan and bend over. “Anus is pink in color and tight,” Dr. Thorn relayed to Dr. Thistle as he pushed a finger against the subject’s tight pucker. “I recommend Serum 8 and 32.” 

“Serums?” Butterscotch’s ears flicked with curiosity. As embarrassing as it was to be standing naked between the two large equines, the batbun felt aroused, the tip of his member peeking out of his sheath. Butterscotch watched as the mare bent over giving him an eyeful of the mare’s thick hips, low hanging pouch, and member as she dug through a cabinet. The batbun let out a squeak as the stallion continued to prod at his hole with a finger, letting out a moan as the digit wormed itself against his prostate.

“Ah here they are!!” Doctor Thistle exclaimed as she stood up two glass vials dangling between her fingers. “Now open your muzzle,” she asked of the moaning mess of a lab subject. The batbun wiggling from the near constant assault on his prostate opened his muzzle, his long fruit bat tongue flopping out. The mare tilted Butterscotch’s head and poured the fluids from the vials down the eager bat’s throat. 

Butterscotch swallowed surprised at the sweet honey melon taste of the mixed serums, his thoughts were interrupted as he smelled the rich musky odor of horse cock as his head was lowered till his snout bumped into the flare of the mare’s cock. Instinctively, the batbun opened his muzzle taking the tip of the horse cock into his muzzle. A satisfied moan from above him encouraged Butterscotch to wrap his long tongue around the head of Dr. Thistle’s member as he felt Dr. Thorn pull his finger out.

“Looks like its working,” the stallion commented as he poked the bat’s hole. The pink ring was now puffy and seemed to be looser. “Everything good on your end?” He asked his sister as he reached between his legs and hefted his log with a hand. 

“MMhm,” the mare moaned as she thrust her member into the batbun’s throat. Butterscotch gagged as the mare’s cock wormed down his tight throat, but to his amazement his esophagus clung around the invading phallus, bulging out as the mare sunk more of her meat into his maw. Dr. Thistle hips pressed against the bat’s nose as she sunk all foot and a half into the wiggling fuck boy. The heavy musk clung to Butterscotch’s senses, deep and rich, intoxicating much like a perfectly aged wine. The batbun drank the scent in, oblivious as the stallion pushed his cock into the pink doughnut with little effort.

“Damn, maybe we should have tried a neutered sub before,” the stallion moaned, his throbbing member sliding deep into the bat’s bowels. Butterscotch squirmed and moaned as the equine siblings rearranged his internal organs. His eyes rolled back as the serums kept him in a perpetual state of lust, all other thoughts besides how warm and right it felt purged with each thrust. 

“Oh fuck, I think you are right,” The mare moaned as hir thick member slide deeper into Butterscotch. Between the pair of equines the batbun was speared helpless twitching as they started to thrust so much he became dizzy. He could feel every movement of the sibling’s cocks as they traveled into his body till he suddenly felt empty as they pulled out. He let out a soft moan as the retreating members were removed from his offices with a wet pop.

“Ok moment of truth will Subject 12 survive?” Butterscotch’s ears perked up as he heard Drs. Thorn and Thistle discussing the results. He was aware of the pair staring down at him as he opened his stretched out muzzle to reassure them he was ok, and that they should continue useing him as a fuck sleeve. Instead as he opened he felt a warm gush of fluid pour out of his muzzle, and only a moment later he felt the same coming from his rear. His eyes drifted down gasping as