Xanadar rose from his place in the corner, cum dribbling from his demonic cock. He ran toward Coal, leaping up onto the now-huge body of his master. Coal let out a soft grunt of surprise as Xan landed on him. It didn't hurt, of course; Coal was now nearly seven feet tall and so thickly-muscled, it would take much more force than two foot tall Xan could muster to hurt him.
"Oh Master, you're magnificent!" Xan cooed, running his little hands over Coal's fantastic, bloated muscles. The infernal familiar pushed and prodded, exploring Coal's greatly enlarged and improved physique, licking up stray bits of cum here and there, purring with satisfaction as he lapped it up. Coal gasped as Xan began to play with one of his big nips; the little demon was unable to reach both at the same time, due to the incredible width of Coal's huge chest.
"X-Xan... wha-?" Coal rumbled, his voice deeper and richer than before. He let out a loud groan of pleasure as he felt Xan's tongue run over his hardening nipple, felt the little demon's mouth clamp on, sucking slowly. "Awww fuckkk..." Coal moaned, as his big dick began to regain some of its lost stiffness. Xan grinned, his prehensile tail lashing out, giving Coal's rising member a solid thwack. Coal gasped in response, his erection swelling dramatically due to the sudden stimulation.
Xan looked back and smirked at the sight of Coal's growing member. "I want some of that, Master..." the little demon purred. Xan eyed Coal's big dick hungrily, stroking it with his tail. When it was sufficiently hard, the familiar launched himself at it, wrapping his small, muscled body around it, squeezing as hard as he could, putting his mouth over the slit, sending his long, pointed tongue deep within. He massaged the thick shaft slowly, reaching down to caress Coal's big balls, running his little hands up and down his master's swollen tool.
Coal's huge body bucked with pleasure as Xan worked him over. Despite having just cum moments before, he could feel another load building. Xanadar could feel it too, could feel Coal's huge cock throb and harden and swell as it was stimulated. "Give it to me, Master..." Xan purred, "Give me that muscle cum!"
"Take it!" Coal bellowed, his whole body stiffening, every massive muscle flexing as he orgasmed a second time, sending a big load rocketing into Xan's hungry mouth. The little demon familiar drank greedily. Although he'd enjoyed the bits he'd licked off of Coal's body, having it fresh from the source was always better! He guzzled down every drop that Coal produced, hungry for more and more.
As Xan drank, his body began to change. The demon familiar's already well-defined muscles began to expand, gaining greater size and girth. A low chuckle arose from Xan's throat, though it was muffled by all the cum he was chugging.
"Oh fuck," Coal moaned, looking up over his huge chest to see his familiar grow. The little demon expanded upward and outward, growing bigger and bigger, muscles swelling rapidly to fill a frame that just kept getting larger. Within moments Xanadar was three feet tall. Then four. Then five. The demon familiar's muscles fantastically thick, hard, and defined, striated and veiny.
When Coal's cock was finally unable to yield another drop, Xan pulled away, somewhat regretfully. The demonic familiar grinned as he looked down at his body though, 350 pounds of rock solid muscle packed onto a five foot six frame. His dick was hard as well, and well over a foot long, jutting lewdly from his hips, above a pair of hefty balls. He turned to look at Coal, dropping down to straddle his master's powerful stomach, his hard cock jutting between Coal's meaty pecs.
"Thank you, Master," Xanadar purred, lifting his arms, proudly flexing his huge biceps. Coal looked up at Xan with wide eyes, surprised at the size his once-small familiar had gained. Coal was still significantly bigger, nearly seven feet tall and packed with pure, massive muscle, but Xan had made great strides in catching up.