Gaster Blaster Transformation Oneshots (ON HIATUS)

Echoes in the Darkness

   Ugh, I've been procrastinating on this...
   Anyway, this one is Gaster Sans (EchoTale) and it was requested by lokiplayz
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   Sans leaned against a tree, blowing out a puff of smoke as he stared off at the sunset. He heard footsteps behind him and he turned around. His gaze rested on Frisk and a smile crossed his face.
   "Hey there kiddo," Sans greeted calmly.
   Frisk waved silently as she continued walking towards the skeleton. Sans chuckled as he walked towards Frisk.
"So what's up?" Sans asked.
"Nothing much. What's up with you?"
Sans shrugged. "Same old stuff as usual."
The tall skeleton put his arm around Frisk's shoulder as he blew out another puff of smoke. He was aware of a slight burning sensation in his chest, but he simply ignored it. He didn't want Frisk to worry about him.
The skeleton and the human went to sit down with their backs against the tree, staring at the final lingering traces of light from the sunset. The sky began to grow darker as the full moon rose up in the sky and stars began to appear against the dark-blue background of the sky.
It was such a beautiful moment... That is, until Sans felt that slight burning pain from before begin to spread through his body, the pain growing worse as the burning sensation spread.
Sans pulled up his hood, trying to hide his face from Frisk. He could feel sweat beginning to form on his skull as his breathing escalated.
"Sans? Are you okay?" Frisk asked.
Sans stood up, stumbling slightly as he fought to stay on his feet. "Y-Yeah, I'm fine. I'm just... tired..."
Frisk looked unconvinced. "Are you sure? You don't look so good..."
"Look kid, I just need some time alone. Just promise me that you won't try to follow me, okay?" Sans huffed.
"Okay, but where are you going?" Frisk pressed.
"Doesn't matter. I just need to be alone," Sans muttered.
   Before Frisk could say anything else, Sans teleported away. The skeleton reappeared in the forest, far away from everyone else.
   He realized that he made a huge mistake by teleporting when he felt the pain grow significantly worse. He grunted as he collapsed to the ground, unable to keep himself on his feet.
   Sans felt like he was falling apart. He felt like he was about to be shattered. He rolled over onto his back and stared up at the treetops. His vision was blurred from the unbearable pain throughout his entire body.
   He was scared... Which was not something that happened frequently.
Suddenly, he let out a grunt as a sharp pain surged through him. He arched his back as he felt his spine begin to snap and twist as it re-set itself. He barely had time to roll back over onto his side before the spikes began to form along his vertebrae, eventually bursting from the back of his jacket as he let out a cry of agony.
   Sans shuddered violently, clawing at his ribs as pain surged through him again. He gritted his teeth, which were rapidly growing into sharp fangs. He felt the fabric of his jacket tear beneath his fingertips, which he realized were growing sharper.
   He cried out in agony as he felt his legs begin to change; his feet elongating and the tips of his toes growing sharper, eventually bursting from the toes of his boots. He screamed in pain, realizing for the first time that his voice was becoming increasingly animalistic.
   He felt a strange tingling sensation in the lower portion of his spine, causing him to turn around. Through blurred vision, he could see a tail beginning to grow out behind him.
   Sans could feel his face beginning to elongate as horns began to emerge along the back of his skull. His vision began to grow darker as he felt the last thread of control he had slip away.

(POV Change)
Frisk wandered out into the woods, calling out for the skeleton she knew and loved. She had already looked everywhere else he would've been.
   That was when she heard a low growl from the shadows behind her. Frisk turned around, relief washing over her as she spotted the familiar golden glow that usually lit up Sans's left eye.
   But her relief was short-lived as a massive skeletal beast emerged from the shadows, his piercing yellow eye peering into Frisk's soul. The human immediately recognized the beast as Sans, just from the cracks over both of his eyes and the holes in his clawed hands.
   But as she looked closer, Frisk realized that there was no recognition in the skeletal beast's eyes. There was only a feral gleam showing that Sans was not the one in control.
   "Sans! It's me, Frisk!"
   The beast snarled as he crept closer.
   "Please! You have to regain control!" Frisk pleaded.
   The beast roared as he charged at Frisk, the determined human dodging at last minute.
   "Stop it! This isn't you! You're not thinking straight!" Frisk shouted.
   The beast's tail flicked slightly as he crept towards Frisk again.
   "Sans, please! Do it for your bro! Do it for me!" Frisk begged, dodging the beast as he charged again.
   The massive beast slammed head-first into a tree, stunning him for a split second.
   "Calm down. You are not this beast. You are Sans," Frisk murmured as she cautiously approached the massive creature.
   He closed his eyes briefly, the feral gleam gone when he reopened them.
   "Frisk?"
   "Sans! I knew you could do it!"
   "What do you mean... Wait, where is my jacket?! And my everything else?! What happened?!" Sans exclaimed, looking around frantically for his jacket, for some reason not noticing that he wasn't in his usual form.
   "I hate to tell you this... But this is all that's left of your clothes," Frisk said quietly as she held up the few scraps of black fabric that remained of Sans's jacket.
   "Fuck..." Sans groaned in annoyance.
   "It's okay. I'll get you another one," Frisk promised, flashing the massive beast a smile.
   Sans chuckled. "Thanks kiddo."

A/N: Sorry this one took so long! I was at Universal Studios Hollywood, so yeah. I had a lot of fun though! :3
Don't forget to leave requests in the comments below!
-Sora