Coal considered making a potion that would break Xanadar's control over him. But within seconds, the idea was discarded; he had never known pleasure like he experienced when the imp fucked him!
Coal perused the potion cabinet, looking at his stock of reagents and special ingredients. He would need to make something special for Xan. He looked over at his familiar, studying him. Xanadar lounged on Coal's bed, his muscular little body resting on a pillow. The imp was watching Coal, a smile on his face, as one of his fingers idly stroked his oversized dick. It sent a shiver of desire through the human.
The smitten young man knew what he had to do. He pulled out his advanced alchemy text, perusing it for the right mix that would make Xan grow until he reached Coal's size. He studied the book carefully, noting the variables that were being discussed. Like most alchemy, there was more than one way to make a growth potion; but depending on the ingredients being used, the results could vary. If he wanted to make a potion that worked exactly right, Coal would have to raid the alchemy classroom for supplies. Coal didn't feel like waiting that long.
Instead, he used what he had on hand, following the recipe in the book, substituting ingredients as directed. He cooked the brew over an open flame, and smiled happily when sparks flew out of it and the liquid turned a deep red color. Coal turned off the burner and poured the liquid from the flask into a cup. He turned to Xanadar.
"Drink this, Xan," he offered, holding out the cup, smiling. The imp sat up, then took flight, fluttering over to where Coal was standing.
Xanadar sniffed the potion, then looked at Coal. "Will this be fun?" he asked.
"Very fun," Coal assured him.
Smiling, Xan grabbed the cup and guzzled the potion quickly, the dark red liquid easily sliding down his throat. He felt a wave of dizziness come over him and fluttered back to the bed, dropping the cup in the process. "What have you done?!" he demanded, as a tremor ran through him.
Coal joined him on the bed. "You're going to love this, Xan," he assured the imp.
Xanadar growled wordlessly back at him, then let out a groan as his body began to spasm. Coal put his hands around his familiar's torso to hold him in place. He could feel his hands slowly being pushed apart as Xan's body began to grow, getting taller and broader, the muscles pulsating, swelling, growing larger to match the body they were attached to. Xan's big cock was rock-hard; Coal wrapped his lips around the tip, slowly sucking the head into his mouth. That sent Xan's growth into overdrive.
The imp's body began to expand dramatically, swelling bigger and bigger, growing beneath Coal. The human could feel the torso he was holding onto push his hands apart, spreading his fingers as the flesh beneath them expanded. He could feel Xanadar's legs grow beneath him as well, pushing him up from the bed. He could feel the dick in his mouth grow, lengthening and thickening as Coal struggled to suck more of it down.
"YES!" Xanadar roared, his voice deeper and richer. He grabbed the back of Coal's head, pushing the young man further down onto his cock, thrusting upward with his hips. His body was radiating power, the muscles bloating with growing sinew. Coal could feel his mouth stretching wider and wider, struggling to accommodate the huge tool within it. The big rod spasmed violently, then sent a huge load of cum rocketing into Coal's mouth. As the human choked on it Xan's body had one more dramatic wave of growth. As the flow of cum subsided, Coal slowly pulled off, surveying what he had done. Xan was much bigger than Coal had intended! The huge imp let out a low laugh, "You weren't wrong, thrall. I did love that!"
Xan pushed Coal off of him and got out of bed, standing up to his full new height. Xanadar was enormous, seven feet tall and at least 400 pounds of solid muscle, maybe more. The imp's dick had similarly-ludicrous proportions, sixteen impossible inches of thick cock. Yet he still had stubby little imp horns on his forehead and little imp wings on his back that looked out of place on the broad expanse of mountainous muscle.