In Universe 10, on the Sacred world
of the kai, the apprentice Zamasu and the Supreme Kai Gowasu engaged in a heated debate over the worth of mortals. The air crackled with tension as their conflicting ideologies clashed, this isn't the first time as they have debated the role of the gods countless times.

Gowasu, ever the wise and compassionate mentor, emphasized the potential for growth and goodness within mortals. He believed that they possessed the capacity to change and evolve, to transcend their inherent flaws and become better beings.

But Zamasu, consumed by his growing resentment, felt an unyielding conviction that mortals were an irredeemable blight upon the cosmos. He saw their sins as an unforgivable stain, polluting the very fabric of reality. In his eyes, only he possessed the clarity to recognize this truth, and he alone had the will to rectify the universe.

As the argument reached its boiling point, Zamasu's seething anger overpowered his reason. He found himself contemplating a dark and sinister plan, one that would rid the universe of the mortals he believed to be sinful. if the other gods are too blind and incompetent, he's not. he will be the one to redeem the cosmos, He decided to take matters into his own hands, with his mind how made up, he feigns a smile and talks with a calm voice.
"My place and destiny have never been so clear to me master, I now understand my true role as a Supreme Kai apprentice, thank you for opening my eyes."

Gowasu takes a breath of relief, Zamasu is a bit too passionate about his role and Justice, he's young and still has time to learn, all he needs is a few thousand years and he'll fully understand the role of gods, and mortals, the old man reassures himself whilst looking at his apprentice.

"Please master, let me make you some tea, something to calm your nerves?"
Zamasu suggests with a sinister glint in his eyes.

The oblivious old man laughs and agrees, one thing that he and Zamasu share in common is the love of tea, Zamasu laughs victoriously within his mind as he thinks.
'foolish old man, this tea will be the last thing you ever sip. if you won't be part of the solution then you're part of the problem, you're unfit and too old. the only good thing you've ever done was choosing me as your successor'

Zamasu retreats to the kitchen to prepare his master some tea, he observed his surrounding to confirm his master isn't close by, he put his hand inside his garments and pulled out a vial of poison, he admires its green glow, and says.
"This is the deadliest poison in universe 10, one sip of it will be enough to make anyone vomit his intestines and die in an instant!"
he gleefully empties the poisonous content into his master's cup of tea and mixes it.

His hands begin to tremble as he pushes the cart. when he arrived, he poured his master a cup, the old man observed the tea and saw that it was clear, this meant that Zamasu's heart was clean as well.

The old man inhales its fragrance and exhales with a satisfied smile.
"Tea made by one pure of heart is unclouded and always the most delicious, this is because tea is a mirror pointed inwards, if the soul of its maker is clouded, it will be as well, but if the soul is pure so will the tea, tea is an extension of the one who makes it."

Zamasu agrees with his master, tea indeed is an immaculate drink, one that only the lips of a god can taste its true sweetness, the love of tea is one of the few things that Zamasu and Gowasu have in common.
"That's true, tea makes right, tea is exquisite, it is the basis of all happiness and Joy."

"Yes, that's true."

"Um... master your tea will get cold if you don't drink it now."

"Oh yes, time to take my tea."
Gowasu takes a long sip and Zamasu's mouth parts with a malicious grin as he waits for his Master to violently vomit his intestines, in another universe this plan would work, his master would die instantly after a sip, but in this timeline, it doesn't, destiny works differently in alternate realities.

'it seems kaioshins are resistant to poison'
Zamasu thinks to himself as he watched his master finish the entire cup, since the poison won't work, he'll have to kill his master the old-fashioned way.

Some hours later when it is nighttime, Gowasu seats alone drinking tea and watching god tube, he takes a long sip and almost choked when he heard a voice behind him.

"you've just sipped your last cup of tea old man"

Gowasu turns and beholds a man dressed in a black outfit, he has green potara earrings on both ears and a time ring on his finger.

"Who are you?"

The man doesn't reply, he simply walked to the old Supreme Kai and takes a seat, then he takes Gowasu's tea cup and drinks up the little that's left of it.
"I am something you helped create." he said "I am Justice, divine justice, but just to be sure I want you to feel my energy."

Gowasu does as the man told him and opens his eyes wide.
"Za... Zamasu?"
he stammered.

"yes Master, that's right, what do you think of this new body? beautiful isn't it? I will use it to make the universe beautiful as well, by doing what you've all failed to do, eliminate all mortals."

"This is unacceptable!"

"the only thing unacceptable is you, so-called gods, who do nothing but fold your arms and watch the very beings you created, the ningens who stain the universe with their sins, I am the light ready to purge the darkness that is mortal kind!"

"and yet you inhibit a mortal body?"

Goku Black closed his eyes with a proud look on his face.
"yes, for I am the true essence of morality and unselfishness, I choose to take upon the sins of mortals, and I'll use that very sin and wipe them all out."

Gowasu felt like weeping, what had caused Zamasu to go this far, hasn't he learned anything from all the years as his apprentice? he sensed Goku Black's heart and realized that he was a madman with a flawed sense of justice that seems right in his own eyes, but Gowasu believes there's still hope, attempting to appeal to his student's compassion he says.
"Zamasu please let's talk this out over a cup of tea, I know you're not evil, you'll always be Zamasu matter how you look, and you'll always be that young Kai whom I found worthy enough to succeed me."

The fake Saiyan opens his mouth to say something, but he hesitates and looks at his master with sadness in his eyes.
"All I've ever wanted was to become Supreme Kai, and help you in making the universe a better place."

The old Supreme Kai smiles warmly and stretches out a hand.
"come to me my child, I can bring you back to the light, please...don't walk the path of darkness, you're not beyond redemption."

Goku Black stares longingly at Gowasu's hand, then he stretches his hand to accept Gowasu's hand, but he hesitates and pulls back, then he closes his eyes and hugs Gowasu, the old kai sighs in relief and hugs his student.

"I loved you Master Gowasu, If I haven't gone this far I probably would have listened to you and found another alternative, but it's too late to go back now. I've already started and it's a sin to start something and not see it through, you taught me that remember?"

Before Gowasu could utter a single word, a ki blade tears through his chest and burst out his back.

Gowasu desperately gasps as he chokes on his blood, Goku Black pushed the blade deeper and whispers into his ears.
"Shh...it's time to put you to rest old man, just go to sleep."
Goku Black pulled back to see the look on his master's face one last time. he saw his old Master look at him with eyes full of sadness, his face that of one betrayed by the person he cares about, but alas betrayal doesn't come from foes but from friends and family. the look on his master's face made the evil Saiyan feel guilty, but his resolve for justice was too strong to let him feel truly sad, Gowasu groans and drops to the ground dead.

Under the cloak of night, Zamasu silently crept toward Gowasu's quarters, fueled by his twisted determination. His mind raced with thoughts of vengeance and Justice, he convinced himself that the deed he was about to commit is a sacrifice for the greater good, He planned to strike down his master in his sleep, removing the last obstacle in his path to reshape the universe according to his twisted vision.

But as Zamasu pushed open the door to Gowasu's room, a chilling sight awaited him. His master lay lifeless on the floor, a look of shock frozen on his face. It was then that Zamasu made a startling discovery-a mysterious figure stood in the shadows, a dark silhouette that radiated an aura of malevolence.

"you wanted to do this yourself right?"
The figure asked before stepping into the light and making his way toward the slightly terrified Kai.

he reached to his ear and removed a green Potara earring then he hands it to Zamasu.
"Congratulations, you're now Supreme Kai."

Zamasu stares at the earring, he had been waiting to hear that from his master for a long time, but he hesitated to look at the mysterious man before taking the earring.

"Who are you?"
he asked.

"I am you."
Goku Black replied.

"how's that possible?"

"It's a long story, but I am you from another timeline where I 'borrowed' the body of the strongest mortal, a body that can endlessly grow in power since mine wasn't powerful enough, this is the body of the Saiyan Goku, but of course, you won't know him because he never became a Super Saiyan God in this timeline and Beerus is still asleep, I seek to pass divine justice across the cosmos, and I will require your aid, this is a call to action Zamasu do you accept?"

Zamasu was taken aback, he never imagined that in another world he would resort to stealing the body of a mortal, but since it was for a righteous cause he doesn't mind, after all, he too would've resorted to stealing the body of a being from universe 11.

Goku Black offered Zamasu his hand.
"come and serve Justice with me, you're the only one capable and worthy of being by my side, after all, you're me, let's destroy all mortals and make our dreams of Utopia come true."

Zamasu looked at where his master lay dead, Master Gowasu would never approve but alas he must follow his heart and do what he believes is just, he nods and they both smiled at each other and hugged themselves longer than a hug should last.

(One Day Later)

The Two Zamasu relax in their garden in Universe 10 drinking tea and discussing their mutual hatred for mortal kind, Goku Black informed his counterpart everything about himself, the Multiverse, Son Goku, and the Super Dragon Balls.

"We must make a flawless plan to ensure we don't fail in our quest for Utopia."
Goku Black says and takes a long sip of his tea.

Zamasu nods in agreement.
"with your raw power and my special abilities, we will succeed."

"that's correct, I'll need you to heal me from time to time so that I can exploit what the Saiyans call Zenkai, it'll increase my strength when I recover from near death."

"very well."

Goku Black grins.
"I have an idea that I think you might find interesting."

"And what might that be?"

"come with me."

The Goku in Black used his time ring to transport himself and Zamasu into space at an unknown period, before them 7 massive orange planetoids float.

The Saiyan in Black gestures toward the orange planetoids and says.
"Behold, the Super Dragon Balls."

Zamasu was awestruck, the glow from the Super Dragon Balls reflect in his eyes as he whispers.

"have eyes ever beheld something so.. beautiful?"
He turned to Goku Black who was staring at him with a sly grin.

"These are the balls I told you about, these things have the power to grant any wish you want,"
Black informs himself.

"I assume you had used it to 'Borrow' the body of the Saiyan for our Project Utopia?"
Zamasu asked whilst still admiring the beauty before him.

"indeed my beloved self."

Zamasu floats towards one of the balls and placed his hand on it, he gently rubs his hand around it, he can feel its warmth and the power flowing within it.
"Since you're the sword, I'll be the shield, I'll wish for immorality."

Goku Black liked the idea, he had planned for Zamasu to steal Vegeta's body but immortality seemed more reasonable.

"read my mind, you'll know the words to summon the dragon."

Zamasu closes his eyes and reads Goku Black's mind, then shortly he opens his eyes.

"it is done."

Zamasu hovers toward the Super Dragon Balls, he spreads his arms apart and chanted with a loud voice

"EmakitaraVinivinavareDinadinare himsahiwi peas and carrots!"

The Super Dragon Balls glow and from it, a supermassive Dragon that makes galaxies look tiny appears with a booming roar, Zamasu admires the majestic creature as it flies around before stopping in front of him, he floats toward the Dragon with a smile on his face.

"Dragon of the gods, I the Supreme Kai of the 10th universe Zamasu wish for immortality."

The Dragon growls in response and its eyes glow, after that, it disappears and the Super Dragon Balls scatter and vanish into space.

"so...how do you feel?"
Black asked making his way toward his comrade.

"I still feel the same, do you think it worked?"

Goku Black creates an energy blade and smirks mischievously. "I guess only one way to find out."

Zamasu told his comrade to stop.
"what if I die?"

Goku Black placed his hand on Zamasu's shoulder and says.
"then I shall mourn your passing and drink tea to your name."

Zamasu opens his mouth to reply but what comes out is a gasp as he feels a ki blade penetrate his chest and into his heart, he looks at Goku Black with a look of shock.

Black smirked satisfied with the results, he pulled out his blade from Zamasu's chest which healed up immediately.
"I guess it worked."

Zamasu touched his chest frantically.
"I didn't even feel any pain." he laughs and looked at his other self.
"don't you want to be eternal as well?"

Goku Black scoffs, if he wanted immortality he would have wished for it a long time ago, but alas the Saiyan pride within him won't let him.
"no need, the power I have is more than enough, besides I prefer wishing for tea instead."

Zamasu chuckles.
"very well then,"

he and Black stood side by side, their plans are now complete and ready to be implemented.
"Project Utopia will come to fruition."