Ryker tightened his grip on the vial in his pocket, a grin spreading across his face as he drew closer to Undyne's house. This was it. His time to make her regret not letting him into the Guard.
   He loosely gripped his sternum as he felt the beast clawing at him from the inside, desperate to get out and show what he was capable of.
   Be patient. I'll give you your chance to prove her wrong. We just need to get there first, okay?
   The fish monster was training in her front yard; perfect for what Ryker was about to do.
   "Hey, Undyne!"
   She paused mid-attack, her ear fins perking up. "...Ryker...? Is this about the Guard again? 'Cuz you're still a shrimp, and the Royal Guard is really... meant for the tough guys, 'kay?"
   His twisted smile only grew wider as he pulled out the vial of glowing orange liquid from his pocket, his spiked red hair falling in front of his right eye as he popped the cap off the vial.
   "'Still a shrimp', huh? I'd highly suggest that you reconsider."
   Without hesitation, he downed the substance in a single gulp, tossing the empty glassware aside once he was finished, causing it to shatter. Undyne flinched, uncertain of what the skeleton was doing, but not liking it one bit regardless.
   Ryker began to chuckle as he felt the marrow of his bones turn to fire, flooding his body with that wonderful searing pain he knew so well. He instinctively doubled over, yet his gaze remained fixated on the fish monster.
   Undyne backed away, her ear fins completely flattened against the sides of her head. Ryker's quiet chuckling quickly turned into maniacal laughter as the pain continued to build up within him.
   "R-Ryker...? You okay there dude...?"
   He broke off in his laughter for a brief moment with a pained groan as he collapsed to the ground, his body shuddering violently as the mutation began to take effect.
   "You're freaking me out here! Wh-What's going on?!"
   "I'm just proving you wrong, Captain Undyne. You can't just judge a book by its cover like you always seem to do." The skeleton's voice was devoid of any true emotion, and a deep, animalistic growl was slowly weaving its way into it with each word he spoke.
   "Dude..." Undyne trailed off as she heard the sound of bones cracking, just as Ryker's skull began to splinter and shift, his nose and mouth distending forward into a muzzle as several twisted horns burst out from the back of his head, his teeth growing into sharp, curved fangs during the process.
   His crazed laughter continued, and he practically gasped for air as it became harder and harder to breathe, his chest feeling as though someone were crushing it.
   He shook his head from side to side, clawing at his newly mutated skull, eventually beginning to leave huge gouges in the bone as claws grew on the tips of his fingers. Tears pricked the corners of his eye sockets, both as an instinctive response to the pain, and as a result of his insane cackling.
   Despite how much it hurt, he still loved the feelings associated with the transformation. The rapid beating of his soul against his ribs, lashing out in panic against the beast that had long since taken root within him, the sensation of his bones cracking and shifting, his joints popping out of place before realigning themselves into a completely new form, the way his body kept expanding and drawing on a much larger mass than he normally possessed... It truly was wonderful.
His voice became deeper in tone, the growl beneath his laughter becoming increasingly noticeable with the longer it kept going. Cries of agony would occasionally cut into the deranged cackling, but it clearly wasn't stopping him.
He arched his back, and the fabric of his lab coat bulged, just before it tore down the length of his spine, a ridge of massive spikes pushing up from his vertebrae and ripping through the stretched-out fabric of his clothes. A tail snaked out behind him, writhing about with a mind of its own as his entire body was wracked with painful spasms.
   Undyne staggered backwards, holding a hand to her mouth as she fought the urge to puke at the sight of the horrifyingly rapid changes. It sounded so painful... yet Ryker made it seem like the damned thing was actually enjoyable.
   The skeleton's grin widened as he saw her expression. "What'ss thhe matterr, Undyne? Arre you sscarred yet?"
   "Dude... This is a bad idea..." She shook her head. "I don't like this..."
   Ryker fell into another fit of cackling, though his voice sounded much more sinister now, especially with the beastly growl that was overtaking his normal tone. Truly terrifying. Yet that's what made it so amazing.
"STILL THHINK I'M A SHHRRIMP NOW, FISHH-BITCHH??"
   Undyne had backed up to a point that her back was against the cavern wall, causing her to jump. Her visible eye gleamed with fear as she stared at the skeleton's convulsing body, which was growing larger and larger with each passing minute.
   Suddenly, Ryker's laughter was silenced, and he coughed a few times as he lost his ability to speak, or make any sound that was even remotely human, his voice box converting itself into a pocket where his blast attack energy was stored. The only sounds that escaped him were animalistic growls that continued to get deeper in tone as he clawed at his skull, the twisted smile never having left his face.
   Finally, after several horrifying minutes, it was over.
   Undyne looked up at the massive skeletal beast that loomed over her yard with a gleam of fear in her visible eye, and her ear fins pinned back against her head. The creature let out a rumbling growl, which seemed to mimic a laugh of some sort, as he crept forward, his tail lashing against the ground before arching over his back, much like a scorpion's tail would.
A soft, red glow pulsated within his abnormally expanded ribcage, presumably from the beating of his own soul. His grin seemed to stretch further across his beastly face as he noticed her fearful trembling.
   She was scared... How perfect.
   That was his goal, after all. To make Undyne, mighty Captain of the Royal Guard, afraid of him, and maybe even regret turning him away from the Guard.
   It was debatable if he succeeded in the second half of that goal, but he certainly made it through the first.
   And that was enough to satisfy his twisted mind.

   Yes, I know I said I wasn't gonna put transformation oneshots in here, but I had to put this one here. XD
   Also, I've been meaning to post this for awhile, but I kept forgetting hnnnnnn—
   But yeah. Ryker's a feckin madman lmao.