Gaster rushed down the stairs frantically as all of the lights in the house were flickering unevenly.
One could hear the power buzzing loudly through the lines and he knew there was only one thing that could cause such a disturbance.

Gaster basically fell through the door of his home laboratory and he hurried over to the experimentation table.
On it, the glass vessel that contained your soul, several cables hooked up to it with careful precision. He quickly detached them from your soul and used his magic to stabilize it.

He didn't know why but your soul proved to particularly tricky to contain. The other souls that were collected didn't show any sign of these symptoms. Not even giving your soul an upgraded version of the container seemed to help.

Gaster leaned over the table, resting his head on his hand as he quietly watched your soul's quivering calm down. Something was wrong and he tried everything in his power to figure out what it was.

Gaster felt awfully protective of your soul and he wanted to make sure nothing ever happened to it until the time arrives for the soul fusion.

A weird noise, as if glass was slowly breaking or someone stepped on thin ice, erupted from the container and he shifted his attention back to your soul, panic immediately engraving on his face.
Slowly but steadily a small crack formed at the edge of your soul and split further towards the center of it.

“What?! No! That is impossible! How-“, he exclaimed loudly. He used his magic once more, his mind racing.

Was the container still not sufficient enough?
Did he make a mistake when he analyzed your soul?

The soul in front of him glowed unevenly as the crack grew a little more. It seemed to be trembling in pain.

He focused all of his efforts on stabilizing the little floating heart and soon, it stopped breaking further.

A small sigh of relief escaped Gaster and he used his magic hands to pick up a stack of papers. He took them into his own hands and flipped through the various pages.

It didn't make sense.

None of it made sense.

Y/N is human.

In front of him sat a human soul so why and how was it so much different, compared to the other souls he analyzed?
Why was your soul behaving so differently?
It was as if the soul was rejecting itself. It was more than evident that something is wrong but why couldn't he find the cause to all of this?
What is he missing?

Gaster sighed and pulled the contained closer, inspecting the small crack on your soul.
It wasn't particularly big, only as thick as a hair. It was barely visible, but definitely there. It was concerning nonetheless.

The soul was glowing rhythmically, occasionally twitching and flickering, another unexplainable characteristic of your soul that it showed whenever it was in its ‘normal' state.

The light somewhat relaxed him in that moment however and his eyes glowed softly in the same color. It made him feel a little closer to you.

His eyes wandered back to the crack and he felt a small pain in his chest. He would never forgive himself if your soul shattered into pieces.
.

.

.

“What are you saying, Gaster..?”, asked Asgore as he bent over slightly to spectate the crack in your soul. His gaze was calm but he looked tired. His nightmare must have kept him awake again. The burden of collecting souls laid heavyily on him.

‘None of the souls that we have collected show any kind of symptoms as [Y/N]’s do. I analyzed everything I could but I found no anomaly. This is very concerning. Especially in regard of the planned fusion.’, Gaster explains as Asgore stood up straight again to look at him.
Asgore sighed and closed his eyes. He knew the weight of this statement and what Gaster was implying. It was a hard decision but it would be safer than relying on an unstable soul.

“You want me to not use her soul for the fusion because of this, correct..?”, asked Asgore quietly and opened his eyes again to look at Gaster.
Gaster nodded hesitantly.

“I have to be honest with you, Gaster…”

Gaster perked up and looked at him:
“I wouldn't have felt entirely comfortable about using [Y/N]’s soul like this. I know it was her wish and I respect that and as king I have responsibilities and duties to follow.”

Agore stops for a moment to take a small breath.

“But as your friend and her somewhat adoptive parent, I feel like this is not the way I would want her to entirely leave this world behind.
And I would also not want her to be part of something that includes…ending other people's lives.
She meant a lot to both of us and I know how much you love her. I wouldn't want to take away from you what is left of her…”

Gaster was stunned by Asgore's words. He wanted to speak up, to protest but Asgore continued:

“I will not use her soul to break the barrier. Not just because it may be dangerous for both of us, but also because she means a lot to me.
...Even if I never got to show her again towards the end of her life…”

Asgore knew exactly what he was saying and what the decision meant for him. He would have to claim yet another soul. To replace yours.

“You can keep her soul.

And don't worry about me. It is the least I can do to repay you for everything you did for me.”

Asgore smiled at Gaster, but Gaster could clearly see that it was also hard for him to have made this decision.

It meant everything to him.

“Keep her safe, will you?”