Gaster never gave them names. Just numbers. The smaller- and 12 minutes older- sibling he referred to as 031. The younger 032. It was a few years ago that the older had learned what the numbers meant. They were the 31st and 32nd subjects of his determination experiments.

The other 30 were dead.

They hated the numbers. Or rather, they feared what they represented. They refused to call themselves that. They only ever referred to each other as 'sibling'. It was enough for the older, but not for the younger. They insisted they needed actual names. So the younger chose them.

Sans and Papyrus.

The older didn't particularly care what they were called at the time, but it grew on them. Gaster was not happy about it at all. Sans had insisted they not tell, but Papyrus chose to tell him, and they did so proudly. The beating they received for it was the worst they had ever taken, but Papyrus would not give in. Those names were their only possessions in the entire world, and Papyrus would not give up.

The experiments themselves were not always bad. Sans loved the intellectual challenges put before them. Papyrus struggled with it. Papyrus hated how stupid they were compared to Sans. Gaster would never tell Papyrus, but it wasn't that they were stupid, Sans was just very intelligent. He had his reasons not to. He was fascinated by the angry looks Papyrus would send Sans' way when the other was excitedly giving Gaster the answer to a particularly difficult question. It seemed that Papyrus was beginning to grow an inferiority complex. Sans did not seem to notice. Gaster had to admit, he was growing to prefer the smaller child. Sans may never be the weapon he had intended, but they made up for it in other areas.

Papyrus, on the other hand, excelled at the physical challenges. Gaster didn't miss the way Papyrus seemed to be trying to show off how much better than Sans they were. When it came to combat training, however, Sans was left out for obvious reasons. Papyrus was a genius when it came to these most of all. They seemed to put forth extra effort in this area, enough to make Gaster suspicious. It didn't take long for him to find out why.

Papyrus wanted to be strong enough to protect Sans and one day escape. It was quite the conundrum. If he stopped teached Papyrus to fight, it would defeat the purpose of creating them. If they were going to be the perfect weapon against the humans, Papyrus needed to know how to fight. On the other hand, it was only a matter of when- not if- Papyrus would over power him.

The worst was always the injections. Gaster had been giving them higher and higher doses over the years, therefore increasing the pain. Unfortunately, there was no 'getting used to' the effects of DETERMINATION being injected into one's soul. There was no way to dampen the pain. There were times he wondered if their souls would give out under the strain.

For Sans, however, the one they hated most was the one they didn't understand.

Gaster would put them to sleep with anesthesia for this one. They had no idea what he was doing, but when Sans woke up they always felt… wrong. Like they weren't all them anymore. Papyrus never noticed this. Papyrus was just happy that they didn't get any injections on those days. But Sans knew something was wrong. It started out with small changes in Papyrus' behavior. His sibling grew more aggressive and quicker to snap. Sans himself began to notice that it was beginning to be harder to let go of their anger. Sans and Papyrus began to argue more and more.

It got worse as they got closer to hitting puberty. It began when they both decide that they preferred to be referred to as 'he'. 'Sibling' became 'brother'. It was then that Gaster decided it was time for the next phase of his experiment. He brought them into a room that was completely empty except for the surprise in the corner of the room.

It was a monster.

The rabbit-like monster was tie in the corner with duct tape over his mouth. He was severely beaten and a quick check of his stats showed that he had only 1 HP left. Gaster locked the door behind them.

"This test will be quite simple," Gaster told them.

"What test?" Sans asked, terrified of the answer. "What's going on?"

"Sans, I want you to kill him."

Sans gaped at him in horror.

"What? No! I refuse! I won't do it!"

Gaster glared at him.

"Than you will die," Gaster answered as though it were obvious. "I have no use for a weapon that cannot fight. You need to build up your LV. This is the only way. Either you kill him, or I kill you. Right here. Right now."

Sans looked back to the shivering monster in the corner. His eyes were wide and tears spilled down his cheeks. Sans felt a rush of rage.

"No," Sans said firmly. "I refuse. Go ahead and kill me. I won't do it. I. Won't. Become. You."

Gaster frowned.

"That… is disappointing."

A Gaster Blaster appeared midair, aimed directly at Sans.

"Goodbye."

The scream that followed would haunt Sans' dreams for the rest of their life. Both looked to the monster that was once in the corner of the room, only to find a pile of ashes. A bone protruded from the middle of the pile, glowing softly red. Papyrus stood facing away from them, breathing heavily.

"P-paps?"

Papyrus took a deep breath and turned around. There was a hard, cold look in his eyes that Sans had never seen before. He took a step back fearfully.

"HE IS DEAD, AS REQUESTED."

"That he is," Gaster replied. The blaster faded away. "That is not exactly what I ordered, but I believe this will do. You should be grateful, Sans, thanks to your brother, you get to live another day."

Gaster directed Sans to the operating table in the lab while he escorted Papyrus to their room. Sans sat in terror of what was to come next. It felt like ages before Gaster returned. There was something in his eyes that made Sans want to run and hide, but he knew that it would be futile.

"It appears that you are not fit to fulfill your intended purpose," Gaster said. "I had thought so since the beginning, so I decided I would use this as a sort of final test, before I repurposed you."

Sans didn't like the sound of that. Gaster smirked.

"I have to say despite it all, I do not mind this outcome."

Xxx

It was several hours before sans was returned to their room. It only contained two cots and a mirror. Tears streamed down his face as he limped through the door. He sobbed when he realized that the two cots, which had always been pushed together, were now separated. Papyrus was asleep on his which he had pushed to the corner of the room. He slept facing the wall, with the only pillow and blanket. Sans' own cot was bare.

Sans couldn't even bring himself to walk over to his cot. As soon as the door had closed behind him, Sans fell to his knees. He didn't make any noise and he wrapped his arms around himself and cried. Why didn't Papyrus just let Gaster kill him? It would have been better than… better than… this!

His soul throbbed.

It was a strange sensation. It wasn't necessarily a bad sensation, but after what had just happened, it did worry him. He clenched a fist into his gown above his soul, but was too afraid to look. He considered waking Papyrus, but was too ashamed. He began to stand with the intention of sleeping with the hope that he would never wake up, but froze. Something in the mirror caught his eye.

There was someone in their room!

Sans gasped! It was a human, of that much he was certain. He also suspected that it was female. She was a few years younger than him, if he had to guess. She was wearing a matching shirt and pants which were blue with little yellow flowers. Her feet were bare. She had tanned skin and dark brown hair. Her eyes were dark brown and almond shaped.

The girl seemed just as surprised as he was. She tilted her head as she looked at him, her eyebrows furrowed. She brought a hand up, facing him with her hand open. Sans walked towards her. It wasn't until he was standing right in front of the mirror that he realized that she seemed to be inside the mirror. Without thinking about it, he brought his hand up and pressed it against where her's was.

They both looked at their hands, then back at each other. Sans was surprised to see that she was shorter than he was, if only by a bit. He'd never met someone smaller than he was, not that he'd met anyone outside Gaster and his brother. Or that ghost they had met when they managed to escape for a few hours. Then the girl did something that took his breath away.

She smiled.

Sans stared at her, mystified. She was the most beautiful thing he had ever seen, even if she was just a figment of his imagination. She moved her lips like she was saying something, but he couldn't hear anything.

"I can't hear you," he said softly, hoping that Papyrus wouldn't wake.

He doubt she heard him, but she seemed to understand. She pouted sadly. She turned away, as if looking at something he couldn't see. She looked back and gave him an apologetic look before walking out of sight. Sans quickly pressed himself against the mirror, as though he could see where she had gone. But it was hopeless.

She was gone.