Jim looked down at his new body and couldn't help but smile. He was a terrible and beautiful sight to behold.
His entire body was covered in the thick black goo, shimmering with a slick wetness even in the dark cave. His muscles stood in stark almost chisled releif, as if he'd been working out for years, giving him definition that any bodybuilder in the world would be jealous of.
Jim stretched his arms, noticing that his hands now had long grasping fingers, each topped with a white dagger-like nail. He glanced down at his feet and noticed a similar change. His legs had twisted and deformed, the knees now bending backwards like a bird, before ending in thick four-fingered feet that were also tipped with long claws. Jim flexed his feet, and grinned, feeling the claws dig into the hard stone easily, scraping long gashes in the floor.
As he grinned he noticed that his mouth felt different. It was now filled with thick dagger-like teeth, so many in fact that he could hardly close his mouth completely. His face had pushed out into a slight muzzle in a vain attempt to contain them all. Jim found it natural to leave his mouth hanging open a bit, long serrated teeth glistening with saliva that dripped down onto an unnaturally long and dexterous tongue that flicked in and out of his mouth, wrapping back and forth as it constantly tasted the air.
Thick black chords of the goop seemed to twist and slide around his body, perpetually pushing out and being re-absorbed. Jim found that he could control them with a thought, easily extending a thick tendril to pick up one of the old skulls literring the cave. The tentacle moved quickly, like a striking snake, and wrapped itself around the skull before lifting it into the air and effortlessly crushing it into dust.
The new being that was Jim grinned even wider as he glanced down at his crotch, thick neck craning and seeming to extend a little as he looked down. His crotch had swelled with virility, two grapefruit sized balls hung low, full of unnatural seed and constantly churned by tendrils that ceaselessly caressed them. A thick sheath extended some ways up his waist, pulsing slowly with pleasure as Jim breathed in and out, holding the promise of a thick cock tucked inside.
Jim craned his neck further as his tongue slipped out and gently caressed the sheath, causing an immense wave of pleasure to wash over him as the package inside shifted slightly.
"Not yet my little pet," He thought to himself, "but soon I will let you out."
With that he began to laugh, a deep sinister chuckle that sounded almost wet and menacing as it bubbled up from his newly expanded lungs. The sound reverberated around the cave as the new Jim enjoyed the feeling of his new body pulsing with pleasure and power. He began to think of what he would do next. No. Who he would do next.
With an inhuman roar Jim lept, lightning quick, from the cave - sticking to the shadows as he ran, nearly invisible in the undergrowth of the forest nearby.
He knew just what he wanted...