Disclaimer: I don't own Aquaman or BBC Merlin, their characters, storylines or related films, comics and novelizations set in the corresponding universes. The franchises are property of DC Comics and BBC One/Shine Limited, and they were created by Mort Weisinger, Paul Norris and Julian Jones, et al., respectively. I am only borrowing them for the purpose of nonprofit expression of personal creative ideas in the same settings.

Full Summary:

"Atlantis has always had a King," said Merlin, a worried frown settled on his features. Arthur longed to kiss his worries away, were it not for the impossible task still ahead. "Now, it needs something more."

The Trident's recovery a constant weight on his shoulders, Arthur returned the intense gaze of his gorgeous companion. "What could be greater than a King?"

"A Hero."

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BBC!Merlin, set in the Aquaman (2018)/DC Extended Universe.

Arthur is a half-human, half-atlantean warrior, popularly known as the Aquaman. Following his world saving feat with his fellow League heroes, he does his best to use his natural abilities for the good of humankind. Enter captivating, fierce Merlin, a Prince of the Seas, who insists on Arthur's help to stop his power hungry half-brother King Mordred from forcefully uniting the oceanic people to conquer the surface world.

The Kingdom of Atlantis needs its one true heir to take the throne, but can Arthur set aside his anger at the people who murdered his Queen Mother for bearing a half-breed? Amid Primordial Creatures, Legendary Weapons and Powerful Sea Sorcerers, Arthur must stop a great war and save everyone, while enduring Merlin's irresistible self.

Easier said than done.

Author's Note: Funny story: after watching Aquaman 2018 (awesome!), I saw someone asking on Tumblr what would Arthur and Mera's ship name be. Merthur came to mind immediately, and this was born. Because Obviously.

Also, I felt I would be terrible at properly writing British English so I didn't even try. I apologize if it seems strange considering the original BBC Merlin TV series, but I hope you enjoy this nonetheless. If anyone wants to help me translate it to the appropriate english connotations, phrasings, wordings and such, you are very welcome to message me.

Be Marvelous, people!

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Chapter 1: Beginnings

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Introduction

As early as Arthur could remember, his mother had been the sun around which they revolved. His father had been a happy man, and young Arthur was the most loved boy in the entire world.

She was beautiful, she was fierce, and she was selfless.

Sometimes, during his darkest moments, he hated her for it.

Once, he had felt like no monster could ever harm him. Ygraine, with an unassailable presence as deep as the ocean, seemed strong enough to chase them off. Uther and Arthur were safe in the knowledge that Ygraine would hold their perfect little family together, forever.

But then she didn't. And the monsters came to take her away.

That terrible day haunted his nightmares, in the shape of loud sounds, blurry images and the memory of the resigned, sad deep sea blue eyes of the woman who meant everything to him.

For Ygraine, born to be Queen of Atlantis, left them behind to return to the place she had escaped from, to a marriage she had dreaded and to a fate she had feared. That place would become her cage, and later her end for the crime of bearing a child of human blood. She did all this, to protect them.

She left, and she took his father's smile with her.

Yes, Arthur had hated her for her willingness to sacrifice herself, for a son that surely should not have been reason enough.

So he grew up, knowing from an early age how dark the real world could be. For the longest of times, Arthur had closed himself off from others and turned away from all he could be.

Willingly.

Bitterly.

Then, the Bat showed up. The League was formed. The world was saved.

And Arthur had named himself Aquaman. No longer hiding, but rather using his strength, his potential, to save those who could not save themselves.

He would never again be that child, unable to stop the inevitable. He would do his damnedest to ensure no other child felt like that.

Thus, a warrior was born.

~0~0~*~0~0~

9 Years Old

Young Arthur had always known there was something fundamentally different in him. Something that set him apart from the other children. Uther had explained, as best he could and after swearing him to secrecy, that the reason was his mother's origins.

Arthur had vaguely understood that Ygraine was not human, and as such he was not either. Not entirely.

But this difference, what his dad said made him special, was not driven home until that school trip to the aquarium.

The cacophony of voices were rejoicing in his presence. Those echoes in his mind came from the numerous sea creatures across the glass. That prideful, protective shark that had aggressively answered his unspoken distress, was now basking in Arthur's attention.

Arthur had been delighted and mystified in equal measure. He could feel a change in the air, which swept around him until it focused on his eyes.

(He would later notice how his own deep sea blue eyes had gained a sort of fluorescent icy blue glow inside his irises. Sometimes they would also glow aquamarine. Uther theorized that it depended on Arthur's moods).

He turned around and looked at his classmates and the other people in the exhibition.

He could see, through the low lighting and on the shadowed corners of the room, certain colors sharpen and others blur. However, clearer in the faces of his peers was fear, of the creatures at his back, of himself, or of the unknown.

It did not matter, for Arthur knew this had changed everything. His blood, once dormant, had been triggered and the prince had come out.

~0~0~*~0~0~

10 to 16 Years Old

Gaius had been a surprise.

Here was another like his mother. A man who had shown up on their dock, clad on a midnight blue bodysuit with a wicked spear on hand.

Uther had been terrified and angry, but had calmed down upon seeing the seemingly proud sea man drop to his knees in Arthur's presence.

Then his dad had been mad at him for coming out, when he had specifically asked Arthur to hide.

Gaius introduced himself as a messenger and advisor to Queen Ygraine. Arthur was delighted; Uther was wary.

That had not mattered for long. Gaius had come to train the young prince on the ways of the sea and he would not be deterred. They started right away.

Arthur's abilities were exciting, and they challenged all he had learnt in school. The human world, Gaius said, was vastly different to the ocean and its folk.

The first few years, Arthur was made to master himself.

Princes of the Sea needed to first know themselves thoroughly: what they could or could not accomplish on their own, to better serve their people. Gaius' words became repetitive after a while, but when Arthur asked how many Princes there were and whether he could meet them, his teacher became evasive and silent.

Then, Gaius came and brought with him another. A few years older than Arthur, Leon was what was called a high born, of noble blood, sworn to serve Atlantis and its throne.

Gaius explained that it was time for Arthur to master others, by way of fighting to be the best he could be.

Leon was, at first, cautious and slightly mistrustful. He appeared to look at Gaius doubtfully and disbelieving half the time. The other half was spent evaluating Arthur against an unknown measure. He seemed to find him wanting.

Arthur, used to the looks his classmates sent him, was actually over the moon. Here was another like his mother but younger, closer to Arthur's age who could possibly understand him better. So they took to sparring together, forcefully at the start but getting skillful with time.

Leon got to know him, and to enjoy his time on the surface. Arthur got a new friend to train with. Brawling, Gaius would say, was no proper way of fighting, but both youths would often ignore him. It was the most fun Arthur ever had.

So Arthur learnt. He swam, he played, he fought. All for the promise of a tomorrow where he would meet his mother, hug her and love her as she deserved.

But promises were meant to be broken. And for Arthur, Atlantis became a beautiful lie that had to be buried, deep in his heart. For who would condemn a woman for loving another?

The quindent was flawless, with a pearlescent gleam. Gaius gifted it to Arthur, from his mother. Another lesson, to master it as someone of royal blood was meant to.

Yet, Arthur had had enough of deterrents and assurances of soon but not soon enough. His mother's weapon, beautiful and deadly as Arthur knew Ygraine to be, was no substitute for her. Thus, he asked one last time.

Leon bowed, disheartened and fearful. Gaius stood proud, firm and stoic.

It was then Arthur knew, before a word was spoken. But, with his heart on his throat, he listened.

The Queen had another heir with Atlantis' King by the traditions of her people?

Arthur had a younger brother named Mordred?

Ygraine was found guilty of betraying her nation by laying with a human and bearing him a son, breaking her marriage vows?

His mother was dead?

Anger and desolation swallowed him, and he was done. No one on the sea kingdom would care for the half-breed son of a betrayer, Queen or not, so why would he care for them?

Leon acquiesced, reluctant but loyal to his Prince. Gaius tried to change his mind but ultimately failed. And his dad? He refused to accept his mom's death, hopeful to the very end. But he accepted Arthur's decision to leave the ocean and everything to do with it behind. Proud of his son, no matter what, Uther still tried to get him to use his abilities for good, as Ygraine would have wanted.

(Needless to say, Uther had been ecstatic at the news that the Aquaman had helped save the world.)

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1 Year Ago

Underwater battle was another monster altogether. Knowing this made Arthur want to slap himself; he really should have let Gaius continue his training, at least until it included this. Well, you lived and you learned.

Steppenwolf was a beast himself; more trouble than he was worth, but Arthur could never really let things go. The outpost had been one of many he had seen through his travels on the ocean, but never approached. He knew what it guarded however. An attack here he could have never ignored.

Also, the Bat's words kept ringing in his ears, the prick.

Saving the life of the pretty, sexy little fish was something Arthur was still on the fence about. Slender, fair-skinned and black haired, the man had probably been someone important judging by the crown he was wearing.

Arthur had let his eyes wander down the figure framed by the tight bodysuit, possibly lingering on the length of those legs...

Then, he about swallowed his tongue when deep blue eyes had flashed gold in the dark ocean floor, and a massive air pocket was created around him and the stranger. Those golden eyes were really something.

The conversation that followed brought out a fascinating - and highly frustrating - amount of sassiness from the stranger's coral pink lips.

The man did not need to convince Arthur to help with the boxes and Steppenwolf. That had been a given. The atlantean armor Arthur asked for, on the other hand, was very useful later.

Arthur had decided to throw his lot with the Bat and the others, and went on to fight a, technically, intergalactic war.

He had seen and lived through weirder things. Although, he never forgot that magical little fish.

~0~0~*~0~0~

Present Day

Uther was calling again. Arthur could never keep track of time zones. He should probably answer, but his head was still pounding from the previous night's revelry.

This quaint little village in the north was one of his favorites. Figured his father could still manage to reach him there. He supposed the Bat had used Uther somehow to find him before.

It had been about a year since the war debacle. He should pay a visit to his brooding, rich friend.

The phone in his pocket vibrated again. Right.

Maybe visiting his home waters first was a better idea. After some more drinking among friends; happy hour was approaching.

"Mister Aquaman, sir!" a young sailor was running towards him. That name had caught on quick.

Arthur thought about jumping into the sea. Maybe he hadn't seen him?

"Wait, please!" the boy was now bent over, trying to catch his breath. What were sailors teaching their young'uns nowadays; no stamina whatsoever. "T-there's been a-an attack!"

"What do you mean? Where?" Arthur asked, grabbing the boy's shoulder and helping him up.

"On the radio, a message came in! A submarine is requesting aid, pirates are attacking them!"

Arthur sighed, scrubbing a hand over his face in frustration. He never could catch a break.

"Coordinates?"

The boy swallowed forcefully and pulled a crumpled piece of paper from his jacket. A couple of older sailors were rushing closer, but Arthur had all he needed.

The blond took out his phone, removed his jacket and shirt, and handed them all to the boy.

"What's your name?" he asked, looking intensely at the youth.

"A-Adrian"

"Ok, Adrian. I'm gonna go now. You, guard these with your life" Arthur requested, patting the boy on his shoulders, hard enough to almost make him fall.

"Yes, sir!" was the enthusiastic response. Arthur refrained from rolling his eyes, and walked off to the rocky shore. He dove, got his bearings and shot off into the open waters. He had a date with some pirates.

~ End Chapter 1 ~