"bro... take the kid and RUN."
He could feel his power surging. It had done this before, but he usually had kept a handle on it. This time, however, Fate seemed determined to make him lose control.
"BROTHER? WHAT IS HAPPENING TO YOU?!"
He groaned. He didn't have the time or state of mind to explain to his bro that if they stayed, they were gonna die. The only thing he managed to force out before his eye exploded in a wave of blue fire and pain was:
"tell undyne... code red."
Then it all went to shit on a triscuit
His power exploded out of him with tremendous force, causing the surrounding area to get decimated. Luckily, Papyrus and Frisk were just outside the blast zone, but if it happened again, they would get caught. Pap seemed to have some semblance of an understanding now, but that wouldn't be much good if he was dead.
He had tears in his eyes as he tried in vain to regain some control over the corona surrounding him and his immediate vicinity. He knew he was powerful, but it scared him that he had no idea just how powerful he truly was. His intentionally lazy lifestyle had blanketed his power somewhat, but that just made this all the more painful. Papyrus was just stood there, frozen in fear as he could only watch as his brother's power tore him apart. Frisk seemed to realize this, and started tugging on Papyrus hand. Sans knew that the kid would help Pap; but right now he had to focus.
He screamed as his power warped and stretched his body into unnatural positions, as it pulled him apart and fused him back together over and over. He tried again to regain control but it was as vain an attempt as the first time. He heard a loud, sharp crack and another wave of pain as his ribs cracked under the pressure his body was being put under. The pitch of his screams deepened as tiny furrows were gouged out of his skull, legs and arms. His left eye socket felt like it was being shattered into tiny pieces as his eye erupted into a fresh inferno, the flames licking the side of his skull and melting into the layer of fire surrounding his body. He was only dimly aware that Frisk had pulled Papyrus out of the clearing, but that knowledge comforted him; the knowledge that his brother wouldn't have to see his rather painful end.
He could already imagine his bro's face. He knew Pap would be heartbroken. He could only hope that the others comforted him and made sure he knew that this wasn't his fault. This would have happened sooner or later. He was just glad it didn't happen right in the middle of Snowdin. There, it would have been a catastrophe. Here, he was the only casualty. It was sad, but not too bad. He cried out as his spine stretched and grew, the vertebrae cracking and splintering.
"SANS! HOLD ON BROTHER!"
It was odd. He thought he could hear Pap. But that was impossible. He was-
"Sans! Snap the fuck out of it!"
He had gone to get Undyne. Sans tried to shout a warning, but it was drowned out by another flare of power and another cry of pain. He couldn't take much more of this. He was going to go insane. His body arched as his SOUL tried to tear itself out of his chest. Then he heard a horrifyingly familiar sound. The sound of his Gasterblasters firing.
Beams started flying every which way. Some went straight up, some went diagonally and others, terrifyingly, flew toward the surrounding treeline. He started sobbing, the pain and fear that he killed his friends wrenching his heart. But Undyne was on the ball as usual, sending a wall of spears from the ground to block any shots. Sans knew that he was reaching his limit, that soon his body would just crumble to dust. And without the confines of his SOUL limiting the amount of power that could be released, all of Snowdin and probably most of Waterfall would be destroyed. It would be like a nuclear bomb, only 1,000,000 times worse.
A white light flashed before his eyes, suddenly it engulfed him and he knew no more.