I'm very excited to see what you all think of this chapter. So without further ado...
Toby Fox owns Undertale and all associated characters.
In the grey, formless void that was the Place Between, Gaster watched over his world. Everywhere one looked, the tiny pinpricks of light could be seen, each representing a world, a dimension, a plane of existence. But Gaster cared only for the one now.
Long ago, he had been responsible for watching over many such worlds, some similar, others very different. He wielded great power, and had been capable of doing far more than observing the realms under his command.
And yet, somehow, he preferred this. This one spark of light that he could focus all of his attention on, watching the mortals below in their everyday lives and struggles. He had little power to directly interfere anymore, but he was content.
"It is beautiful, is it not?" he asked quietly, smiling down at one large building in particular, watching Monsters and Humans celebrating together in harmony.
"Yes, it is."
Gaster turned slowly. He had not actually expected an answer to his question. His gaze fell upon a large glowing ball of bright white light, nearly as large as he himself was. Despite having no features, Gaster got the impression that it, too, was looking down at the world.
"Such beauty in life," the light continued. "The mortals experience it in a way we never will. Their flaws, their imperfections… their struggles and hardships. It all weaves together in a glorious tapestry that we could never create. The imperfections… are what make it perfect." The light was silent for a moment. "A truth that Exilus never comprehended."
"He no longer calls himself that," Gaster murmured, turning back to the world he protected.
"Yes. An indicator of how far he fell. The Defiler, one who would enslave all reality to his will, and mold it into his image. He saw reality as nothing more than his plaything, and the concept of free will…"
"Is infuriating to one who strives for perfection."
The light pulsed slightly in agreement.
"Yes."
The two watched in silence for a few moments, until Gaster finally spoke again.
"I did not think we would meet again."
"We had not intended such," the light admitted. "However, The Defiler finally overcame his pride, and conquered the last barriers that prevented him from retaking his power. We could not allow that."
"You broke your oath, then?" Gaster questioned.
"We were not to interfere with reality. But he was not part of the reality we created. And had he become one of us again, he would have destroyed everything beautiful of our creation. To not act would have been the the greatest betrayal of our vow."
"I heard his death-cry," Gaster admitted. "Though I feared it was a trick to catch me off guard. He is truly no more, then?"
The light bobbed up and down sadly.
"Yes."
Gaster was silent for a time, then spoke softly.
"He ever did mistake domination for power. Though I wish he could have been dissuaded from his folly."
"Not even we are above such fallacies. This is why we do not interfere with creation. Even if we were to do so with good intentions, we would be unable to keep from tainting it."
Gaster looked back to the light.
"If he has been destroyed, what became of the rest of the Exiled?"
The orb pulsed softly in slight amusement.
"They have been imprisoned… on a world they created, by the mortals they sought to enslave. We could not think of a more fitting punishment than this."
Gaster simply nodded, folding his hands beneath his robe, and continued to watch the light. He knew there was another reason his creator had come here, and he was content to wait until they told him why.
He did not have to wait long.
"Gaster," the being finally said. "There is great darkness in your future. If you remain here, the day will come when you are destroyed in defence of your world. We would give you the opportunity to avoid that fate.
"When we return to the edges of reality, we would take you with us. Long have you served us, and even longer have you watched over and protected our creation. You have earned your peace tenfold, and we would see that you receive it."
Gaster blinked, caught off guard by the light's proposal. He turned his attention back to the world below. He had never considered that he might one day return home, never thought he might be asked to do so.
He would still be able to watch over the world from there. He remembered the glittering tapestries that encompassed all of reality, all of creation. He would be surrounded by light, once again removed from the cares and burdens he had been carrying for so long. He would no longer be alone.
If the husk of his former master no longer threatened his world, would it not be safe for him to leave? He turned back to the being that awaited his response.
"If I fall defending this world… that means there will be something that threatens it again in the future. I cannot leave them alone to face that. If I must sacrifice myself to keep them safe, then so be it."
The light emitted a small hum of approval.
"Ever do you exceed our expectations of you, Gaster. We would have you know, we delight in your actions, and take pride in your accomplishments."
Gaster inclined his head respectfully.
"Thank you, but… I have only done as you created me to do. There is no need-"
"Gaster," the light interrupted softly. "Do not believe that your decisions, your actions, have had no consequence. We gave you life, you chose what to do with it. You chose to live up to your potential, and exceed it, just as Exilus chose to throw everything away for the sake of temporary power. We did not write the script… we merely set the stage."
"You honour me," Gaster murmured in response.
The light turned its attention back to the world.
"A piece of his soul still remains here."
Gaster focussed his attention on where the light was looking, and saw Chara, the robotic girl with one leather-wrapped arm draped around the newly-visored Kid's shoulders. The girl whispered something into the reptile's ear-hole, and they both snickered.
"Without him, she is no different than any other mortal." Gaster replied. "She is as much a part of this world as those who were born here. In death, Exilus has given the fragments of his soul a new, and better life."
The warm glow of the floating orb pulsed slowly in silent agreement.
"Despire his wish to destroy, he could not help but to create. A warning, we think. But for who?"
"A warning, a lesson, a hope. It is incredible how one thing can mean so much more than first glance," Gaster smiled. "Is that not what you taught me?"
"Yes." The light was quiet for a moment, then said;
"Gaster, before we go, we have one more thing we must tell you." The light seemed to fade slightly for a moment as Gaster turned back towards it, then it spoke quietly.
"One day, a child who is both Human and Monster will come to your world. When that day comes, give them this message..."