CrystelTheWolf I blame you for this one.
This one is not a request, but one inspired by the Saw movies. I have only seen the first one, so I don't necessarily know of all the traps, but I know enough to create one of my own.
   I know this will not be 100% accurate, since Sans has gone through several traps in this case, but y'know what? It doesn't have to be exactly like the movie! That's the beauty of fanfiction, am I right?
   Also, since this is based off of Saw, I created my own trap for this oneshot.

This is it. It's described more in the text, but this is kinda more of a "visual" representation of it. Image was hand-drawn and digitalized by myself.
   Anyway, enjoy twice as much suffering for the skeleboi! >:3
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Sans awoke with a jolt of fear, looking around the darkened room and anxiously awaiting his next challenge. He'd been through countless scenarios, each one more horribly painful than the last.
How many different timelines did he lose his own life in? How many times had he failed the assorted tests? How long had he been here? How much longer would he remain trapped in this hellish nightmare of a place?
He heard the rattling of metal chains as a cage was lowered from the ceiling above, a soft whimpering sound coming from within.
Sans felt his soul skip a beat as he instantly recognized the voice behind the pitiful sound.
"Sora! No! Not her! Please not her!" Sans screamed, his voice hoarse as he called out to whoever was behind these horrible challenges.
   "S-Sans..." Sora's voice was weak, but it was definitely her.
   Sans's gaze snapped up as a tv screen was lowered from the ceiling. On the screen was a creepy looking puppet, sending chills down Sans's spine.
   "Greetings Sans. You don't know me, but I know you. In fact, I do believe we've been through this quite a few times, am I correct?"
   "What the hell do you want from me?!" Sans howled in anger, his left eye flaring blue.
   "I want to play a little game with you. As you can see, your precious little Sora is rotting away in that cage over there. There is a trap in that cage, set to go off in 30 minutes."
   "You let her go! You sick bastard!" Sans snarled, clenching his fists angrily.
   "When that time expires, the device around her chest will clamp down, crushing both lungs, her heart, and basically cutting her in two. But you can save her."
   "Tell me how dammit! Please! I can't let her die!" Sans pleaded, his gaze desperate.
   "There is a key implanted into your soul. You will have to tear open your own soul to get to it. Both you and Sora will live if you get through this. Remember, you have 30 minutes. Good luck."
   Sans growled to himself, pissed off that someone could even bear to do this to his little angel. "Don't worry Sora... I'll get ya outta there... Dammit... I gotta get to that key..."
   He glanced up at the clock, remembering with a jolt of panic that he only had 30 minutes.
Shit shit shit shit SHIT!
   Sans glanced down at his chest, his soul pounding frantically within his ribcage.
Wait... That means... Oh shit...
   "Okay... Don't worry, my little angel! I'm gonna get ya outta this!" Sans's gaze trailed back to his chest, the skeleton wincing as he really considered what he was doing.
I really hope this doesn't get any uglier than it needs to be...
He didn't even have anything to aid him in what he was about to do. No knives, no scissors... Nothing that would make his job so much quicker and easier.
Oh well... No pain, no gain, I guess...
He called his soul forward, the blue heart manifesting in front of him. He clasped his hands around it, trying to figure out where to start with it.
He inhaled deeply, trying to calm down. "Okay... Here goes..." Sans held his soul in the palm of one hand, preparing to do what had to be done.
Without a second thought, he pressed against the surface with his fingertips, gritting his teeth as he did so.
"C-Come on... I-I have to do this..."
Sans pressed harder, hoping this wouldn't end in his soul simply being crushed. Pain rippled through him, making it harder to concentrate.
He grunted, continuing to press against the glowing blue heart before he finally managed to puncture the surface of his soul, crying out in agony as he did so.
   Dark blue magic trickled from the wound, running down his hand and leaving a distinct blue stain on the bone. A sharp pain spread throughout his body, the source being at his chest.
   But he couldn't stop there. He had to keep going. He had to get to the key to free Sora.
   God, this would be so much easier if I had something sharp to work with here...
   Sans tore at the puncture wound with his fingertips, wishing he had the energy to shift forms ever-so-slightly, at least to a point where he had claws. Each strike against his soul was like being cut with a blunt knife.
The skeleton was shuddering so violently that his bones were rattling. Sweat ran down his skull as he fought to stay calm. He panted heavily, straining against the pain that threatened to take his sanity.
   He glanced up at the clock, a new wave of fear flooding over him as he realized he only had 20 minutes left.
   Sans continued to claw desperately at the surface of his soul, frantically trying to get to the key to save Sora.
   He hadn't even realized that he'd begun to slowly change forms until he noticed that he was actually starting to do real damage to his soul; now leaving jagged claw marks where he tore at the blue heart as opposed to the slight grazes he'd been inflicting before.
   He paused, shakily raising his hand to look at it. He broke off with a shudder as his worst fears were confirmed; he was shifting, and at what was probably one of the worst times possible.
   Wait a sec... I can use this to my advantage! I just have to fight it enough to get through this with a relatively clear mind. Then it'll be over before I know it.
   Sans took a deep breath before suddenly stabbing into his soul with his newly-formed claws, choking down a cry of agony as he did so. He dragged his claws down the dark-blue heart, his vision blurring from the excruciating pain resulting from his actions.
   He didn't stop until he'd opened up a massive cut in his soul, blue magic now gushing from the fresh wound and dripping down onto the ground at his feet.
   His breath was coming in short, ragged gasps as he desperately tried to remain in control. Not thinking straight, he continued to claw at the huge tear, making it deeper and deeper until he reached the very center of the heart.
   His chest felt tight; he could barely breathe without an intense pain shooting through his entire ribcage. His body felt limp.
   Magic dribbled from the corners of the skeleton's mouth, as well as from his eye sockets. He finally managed to gather enough strength to plunge his hand into the deep gash in his soul, barely holding back a scream as he did so.
   A wave of nausea came over him as he felt around for the key within his now mangled soul. After a few moments, he managed to pull it out, his hands shaking uncontrollably from both the pain and his own fear.
   He chuckled weakly, flecks of ice-blue magic spraying from his mouth as he did so. "I-I got it S-Sora... I-I'm comin' ta s-save ya..."
   He willed his soul to return back to its rightful place within his ribcage before he stood up, his hand tightly gripping his sternum as he stumbled over to the cage, almost as though he were drunk.
   "Sans... hurry..." Sora pleaded, her voice strained.
   "D-Don't worry, s-sweetheart... I'm comin'-" Sans suddenly cut off with a grunt, doubling over in response to a sharp pain that surged through his chest.
   "Sans!" Sora screamed, reaching out of the cage with a bloodied paw.
   Sans gritted his teeth and somehow managed to pull himself back together. "I-I'm fine... D-Don't worry...
   The skeleton finally made his way to Sora's cage, sweat pouring from his brow as he shakily pulled the key out of his pocket.
   He tried to use the key, but found that it didn't work with the lock. "Urgh... M-Must I do everything the h-hard way?"
   He realized that he would need to use his claws to pick the lock. As he tried to pick the lock, he found that he was almost too disoriented to do so. "C-Come on... P-Please... For S-Sora..."
   He finally managed to unlock the cage, but he suddenly stumbled backwards, falling to his hands and knees as the door swung open.
   "Sans?!" Sora squeaked, rushing out of the cage to Sans's side.
  He moaned in agony as pain began to ripple through his entire body, the skeleton not even entirely aware of what was happening around him as the transformation he'd been fighting finally began to take its hold.
   For the first time, he noticed a large splotch of dark blue staining the fabric of his shirt, right where his soul would be.
   Shit... Maybe I shoulda healed before putting my soul back...
   "Sans! Sans, say something!" Sora chirped frantically, her eyes turning dark blue with a hint of pale gray as her joy to see her boyfriend turned to a mixture of fear and concern for what was going to happen next.
But could I have actually healed? Would this hellish game actually let me do that?
   The dragon grabbed ahold of Sans's shoulders and began to violently shake him, attempting to snap him out of his unresponsive state.
I guess the point of all this was to see how much you'd sacrifice to save something... In my case, it was whether or not I would tear myself apart to save my girlfriend...
   Sans groaned, collapsing to the ground as pain tore through him once more. He began to shudder uncontrollably as he felt control slipping from his grasp.
Assuming I was forced to sacrifice pretty much my own well-being to save her, I don't think I'll be allowed to heal...
   Through the foggy haze of pain, Sans felt himself being rolled over onto his back and lifted into Sora's embrace. That usually would have been comforting, but at that moment, it just seemed to cause more panic.
   His wounded soul pounded in his chest as Sora pulled him closer. She said something to him, but the sound of her voice was warped; distorted beyond the point of comprehension.
Before he knew it, Sora was trying to help him to his feet, allowing him to lean on her as she guided him away from the cage.
   Without warning, Sans doubled over with a moan of anguish, his arm tightly grasping his ribcage as pain surged through him.
Sora, seeming to catch onto the fact that her friend was suffering, decided to sit down and allow Sans to somewhat calm down. Despite this, the skeleton found he couldn't fight off the paranoia that had been gradually taking control of his actions.
   Then he remembered why he needed the key. It wasn't to unlock the cage; it was to disarm the trap set to kill Sora.
   He shakily fished the key out of his pocket before attempting to hand it to Sora. "S-Sora... Y-Ya gotta unlock it y-yourself..."
   The dragon took the key, reaching backwards to try to disarm the trap. "Sora's arms not reach! Can't get key into lock!"
   Sans groaned in agony, falling forward onto the ground and burying his face in his sleeve instinctively. After a few seconds, he took a deep breath and managed to sit up and take the key from Sora. He scooted closer to her, attempting to steady his movements enough to be able to disable the trap.
   Dammit... Too fucking disoriented for this...
   He gritted his teeth and smacked the side of his skull with the palm of his hand, trying to refocus his scattered thoughts. Sora flinched, but said nothing.
   Sans inhaled sharply before trying once more to disarm the trap. He strained against the pain that threatened to drive him to insanity, until he finally managed to succeed in his task.
   The trap around Sora's chest opened up and fell to the ground with a loud clang. Sans fell forward onto Sora, the strain of trying to hold back what he knew was inevitable starting to take its toll on him.
   "Sans?" Sora squeaked, her eyes turning dark blue with concern.
   Sans grunted softly, wincing as he felt a sharp pain in his spine. "S-Sora... W-We gotta get outta h-here... Before w-we lose the ch-chance..."
   "That's what Sora trying to tell Sans! Can escape now! Sans succeed in getting Sora out of trap!" Sora chirped, her ear twitching.
   "I-I can't do it alone... I c-can't walk... I n-need you to h-help me..." Sans murmured, his voice hoarse.
   Sora took a moment to consider her options. "Stop fighting..."
   "S-Sora, I c-can't... I might h-hurt you..." Sans broke off with another grunt, his eye flaring blue for a split second.
   "It better than what happen now. Even if we get stuck here, Sans can break out, right?" Sora continued.
   "I-It's not worth it... I'd k-kill you before we escape..." Sans argued, wincing as pain shot through his spine once more.
"We not have choice! Sora can't carry Sans all the way!" Sora protested, her eyes flashing orange for a brief instant.
Sans opened his mouth to speak, but the only sound that came out was another gut-wrenching moan as pain seared through his entire body. "W-We don't have t-time! I don't have t-time! Sora, p-please!"
   "It go faster if Sans give in! Escape faster if stop fighting!"
   "S-Sora-" Sans cut off with a cry of agony as he curled in on himself. "You're n-not helping!"
   "Well Sora trying, okay?!" Sora retorted, narrowing her eyes. "It not like Sora been in this situation before!"
   Sans inhaled sharply between his teeth, which were rapidly growing into large, curved fangs. "W-Well I have! So t-trust me on th-this!"
Sora glared angrily back at the skeleton before her gaze seemed to soften slightly. "Look, Sora know Sans hurting. But what Sans going through now is less painful than what we face if we not get out."
Sans huffed, his eyes narrowing. "Wh-What are ya tryin' ta g-get at here?"
"Sora saying that Sans need to stop fighting against something that can't be stopped. And the more we sit and argue, the less time we have," Sora explained.
"W-We already won the d-damn challenge! Wh-Why would we still be p-pressed for time?!" Sans snapped.
"We not know what happen if win challenge! We not know if puppet man let us go, or throw another challenge at us! So we need to get out while we still can! Sans not listening!" Sora squeaked defensively, the ridge of feathers along the back of her head standing on end.
   "S-Sora, just stop-" Sans broke off mid-sentence with a cry of agony as he felt his spine beginning to snap out of place, new vertebrae forming between already existing ones as his spine began to distend.
   "What? Stop what?"
   "Dammit, I have th-this under c-control! I d-don't need your h-help!" Sans snarled, his voice gradually becoming deeper and raspier as he spoke.
   Sora's tail flicked side to side in agitation. "Sora just trying to help..."
   "And I understand th-that. But I d-don't need you to g-get in the way. I-I don't want you-" He cut off with a groan as the pain spread to his legs. "I-I don't want you to get h-hurt..."
   Sora fell silent, the gleam in her eyes growing dull as she stared down at the floor. "Sora sorry..."
   Sans could feel the changes beginning to affect him all at once. Massive spikes pushed upward from his vertebrae, tearing through the fabric of his worn-out blue jacket. His feet had begun to splinter and shift, rapidly changing from their usual plantigrade structure to a completely digitigrade structure.
   While some of the more major aspects of the transformation took place, a few other minor things were going on at the same moment. He had begun to grow a tail and his skull was beginning to change as well.
   His face was stretching outward into a long muzzle while horns began to sprout from along the back of his skull. He instinctively started clawing at his face, the feral side of his consciousness beginning to take over his actions.
   Sans howled in pain as his ribcage began to expand, all while the rest of his bones started to distend and thicken all at once. His body was beginning to draw on a mass it didn't normally possess.
   Eventually, the transformation died down, leaving Sans towering over Sora, who was trying to stay brave, yet was absolutely terrified on the inside.
   "S-Sans?" Sora squeaked, her voice shaking.
   Sans sighed, his gaze softening. "Sssorrra... I'm sssorrrrrry..."
   Sora chuckled, reaching up to pet Sans's muzzle with her paw. "It okay. Sora still love you."
   Sans grinned, his tail twitching. "I love you too."
   "Sooo... How we get out?" Sora asked.
   "Therrre'sss an exit overrr therrre," Sans rumbled, pointing towards a huge metal door that was thrown wide open, as if waiting for them to exit.
   "Okay! Let's go!" Sora chirped, racing over to the door.
   "Wait up! I'm not fassst like you arrre!"
   "Yes Sans is! Sora ran from Sans before! Sans almost catch Sora!" Sora argued, her ear flicking.
   "Keyworrrd almossst. I didn't actually catch you. Even like thisss, I'm ssstill a lazybonesss. Nothing can get rrrid of that," Sans pointed out before following Sora to the exit.
   The two monsters left the room, neglecting to talk about what they'd been through and instead choosing to laugh about past memories. As far as this was concerned, both of them just wanted to forget this all happened.
   Maybe it would be a story for another time, but today wasn't the day to revisit it.

A/N: Fun story, right? XD
   Sans rips apart his own soul to save Sora... God, that was fun.
   Anyway, sorry if you didn't like all the Sorans in this chapter. I couldn't help it. :P
   Plus, ya know what? This is MY oneshot book, not yours! I get to do non-requests sometimes! And right now, I'm in the mood for some very angsty, Saw-based Sorans stuff! So fite me, haters!
   I'll move onto actual requests eventually.  But I really want to do my own thing for awhile, ya know?
   But, hopefully this tides you guys over until I can write another part (maybe an actual request this time? XD). For now, stay determined!
   -Sora