All rights belong to Akira Toriyama, Toyotarou and Toei Animation
This is based on the manga cannon, so there may be some discrepancies with the anime.
The four found themselves around Bulma's kitchen table, discussing the situation in the late morning sun which shone in through the large windows. It was such a contrast to the oppressive darkness they had been subjected to, with flowers in a vase on the table, stick-figure drawings Trunks had made as a small child and photos of the family stuck with magnets to the refrigerator. Yet Bulma's happy house had been headquarters in a number of dire emergencies. She was currently in her lab working, having ascertained that her husband had not died in the interim.
Vegeta was unaware of how harshly he was glaring at those innocent flowers, his mind elsewhere. Kakarot had been a right nuisance on the way back; not in his usual happy-go-lucky ignorant way, but he had instead been incredibly irritable. Vegeta knew that this Darkness was responsible for the differences between the saiyans of universes 6 and 7, the reason his race was so bloodthirsty and ruthless.
But he didn't know how long it took to take effect.
Or if its effects faded.
What if he suddenly reverted to type, right here in his wife's kitchen?
"So…I guess that didn't work." Kakarot broke the silence.
"Indeed." Vegeta replied, mind still lurking in the depths of disquiet. He didn't want to go back there, again. Didn't want to be trapped in the oppression of loathing and wrath.
"But why didn't it work?"
"I suppose it may have become used to the technique," Whis suggested, "It was imprisoned before, after all."
"It was?" Kakarot asked, curious.
"Yes." Whis answered.
"But not in a container," Vegeta interjected, then immediately regretted it. He didn't like to raise the issue if he could help it. They might decipher him, and finish off what his father had failed to do.
"That's right. You said it was a fusion, didn't you?" Whis clarified.
"Yes. Keel Vegeta fused with it."
"How?" Kakarot asked, "I mean, it doesn't have ears and it can't do a dance. Is that thing even alive?"
"Yes." Vegeta answered, again before he could stop himself.
"But how do you know?"
How did he know? It was already inside him, like a parasite, wallowing, imprisoned in his soul.
"I just do!...Couldn't you feel it, insinuating evil inside you?" He didn't need to give them the full details.
"But how does one fuse with a gas?" Whis mused.
Kakarot sat up with a gasp.
"I could go and ask him! This other Vegeta, he's in the Other World, right? He is dead, isn't he?"
"He died, yes." Vegeta confirmed, "The fusion killed him. But you won't be able to find him."
"Why not?"
"Saiyans are reincarnated, Kakarot. When we die, we come back as another saiyan."
"Isn't that just your belief system?" Beerus asked.
"No. We are reincarnating creatures, just like our god. We had ways of discerning one's past incarnations. Our middle names are in fact our strongest incarnation. It wasn't just a belief system at all. So Keel Vegeta no longer exists. His memories are gone."
His whole self was gone, replaced by someone worth far less. Someone unworthy to hold his title as a middle name, Vegeta often thought.
"Bummer." Kakarot put it eloquently.
"Wait…" Beerus began, looking askance at Whis, "Couldn't you use your staff? To watch what happened back then?"
"You can see the past?" Kakarot cried out, an embarrassing smile on his juvenile features.
"I can indeed see the past in this orb on top of my staff," He confirmed, "I can even project the images for you. I'm afraid that I cannot adjust the volume. Do you have a nice, clear wall I could use, Vegeta?"
"Er…yes."
Vegeta led the group into the lounge, removing the TV unit from its place to make a clean space for Whis to use. He couldn't believe he was about to watch a home movie of Keel Vegeta himself. He had been raised on the stories of their god and his many incarnations, especially the ones of Keel Vegeta. Popularly hailed as one of the strongest and longest living incarnations, his place in the saiyan's historical pathway was especially important given his involvement with the Great Darkness.
It still rankled him that Kakarot didn't bear his own saiyan name with more pride, given his namesake was Keel Vegeta's top disciple.
As the inappropriately named Kakarot flopped inelegantly on the couch, Vegeta sat much more sedately, his eyes fixed to the blank wall on which history was about to be played.
Whis tapped his staff once on the ground, and a cone of light spilled out from it onto the wall. At first, it was a simple white, but this eventually focused into an image.
And then he could see him, Keel Vegeta himself!
"Hey, Vegeta, he looks like you!"
He did indeed look like the modern-day Vegeta, with ebony hair sweeping upwards in the royal style, and the same piercing eyes and strong brow. The nose, ears and mouth sported subtle differences, and he appeared to be shorter. He was wearing a long, red coat over the traditional armour of Sadala, but his clothing and boots had seen much wear and tear. Vegeta recalled that the fighting in the months leading up to his great sacrifice had been fierce.
The famous saiyan halted in an abandoned field, surrounded by upturned dirt and craters, no other life form to be seen.
Except for the familiar black mist which permeated the atmosphere, tainting everything it touched.
Keel Vegeta (it was rude to call such a high ranking personage by his first name alone) spread his arms out on either side of him, reminiscent of Vegeta's own final flash. Face twisted with concentration, the other Vegeta began to growl low in his throat. Almost immediately, the air around him grew thicker, with more and more particles of the Darkness being attracted towards him.
Somehow.
"What is he doing?" Kakarot questioned, but neither Vegeta nor the godly beings which joined him could answer.
It was just like the failed mafuba, with the Darkness being pulled towards the saiyan until he could no longer be seen at all.
"Grr…how are we supposed to know what he's doing?" Beerus complained, "This is telling us nothing."
"Actually, now we know we have to stand with our arms out and start yelling." Goku objected.
There was something to the yelling, though. It was changing. Not the kind for charging up power or wrestling with strong opponents but
"He's in pain." Vegeta realised.
But of course he was. The whole process had killed him.
They were sitting there, in Bulma's living room, watching someone die, or more correctly, listening to it.
And it was only growing worse. Keel Vegeta was taking great, ragged gulps of air, screaming with such force that his lungs must be turning inside out. Vegeta couldn't imagine the kind of pain they were witnessing, the kind that would make someone shriek so horrifically.
Even Kakarot had gone pale.
"I'm glad he doesn't sound like you, Vegeta," he confessed softly, before continuing more loudly, "Why is the fusion hurting him?"
"I would surmise that his body is now the battlefield between his soul, determined to imprison the Darkness, and the Darkness, determined to escape."
"Gees."
Eventually, though, the black mist thinned until they were able to see Keel Vegeta clearly.
And even the battle-hardened saiyan prince felt nauseous.
Keel Vegeta looked like a broken toy that had been dropped in spaghetti. His skin was caked in blood, which had flowed from his mouth, nose and even his eyes. Shattered bones had split through the skin of his legs, arms and chest, poking out into the dawn air. The armour which he had worn so proudly was scorched and torn, pieces scattered around him. Even his toes, exposed with the deterioration of his boots, looked mutilated.
"Oh my," even Whis was moved.
Vegeta was surprised the battered husk was still standing, but it wasn't for long. His knees buckled with a strangled wheeze, and he toppled onto the blood-soaked ground, facing the early morning sky.
They watched in silence as he drew his last breath, and the light faded from his still open eyes.
"He's dead," Kakarot commented unnecessarily. "Gees, that was…Did we have to watch that?"
"That is how the Darkness was originally sealed away. That is how it might need to be sealed again."
"But how?" Beerus grouched, "What exactly did he do? We can't just go back there and stick our arms out!"
"I think…" Kakarot began, "it might have been a version of the mafuba. Except, he was using himself instead of a pot."
The idea of Keel Vegeta being compared to a piece of pottery was insulting to Vegeta's saiyan sensibilities.
"Perhaps," Whis conceded, "It would allow him to constantly exert energy to keep the Darkness confined, rather than relying on the container to do that work."
Whis cancelled the image of the disfigured corpse, finally letting the poor saiyan lie in peace, and began searching for something in his fancy, magical orb. That thing sure was handy, Vegeta mused.
"There must be another way…" Kakarot muttered, fist to his chin in thought.
"Well, if there is, you'll have to think of it quickly. The Darkness isn't far from earth."