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The kingdom of One for All was a thriving paradise. A symbiotic relationship between the Mer citizen and the human citizens brings trade far and wide. The amazing sights and infrastructure of both human and Mer societies bring guests and visitors from far and wide.
The magic of the Mer and the budding inventions of the humans come together for what people like to call a new Atlantis, the name becoming more and more popular amongst the citizens—proudly calling themselves Nuevo Atlanteans, the Mer’s and their pods rejoicing, as well as the humans in their villages.
They were welcomed, by their human compatriots, with open arms. Their forms are able to shift between their scales and tails and their human form – being descendants of the old Atlantis. As they shifted to an amphibian lifestyle, the mers forget the dark and deep oceans. The terrors of the deep, those who never forgot the fall of Atlantis, and the forced change placed on those humans who thought themselves, gods.
The Dragons of the deep and the dragons of the summits remember the folly of their human companions. The seven rulers of All for One ruling equally and fairly, even though one of them was never able to leave the ocean. His own sea dragon nature forcing him to stay under the water as the true inheritor of the moon and the sea.
It was him that the rest of the rulers feared, his own nature different from the rest. Despite his mighty power, he was weak. He stayed out of the moon and hardly travelled with his kind. Small for a Dragon so young.
The other rulers carved a cave out deep in the sandstone below their human castle, deep and dark enough that the dragon would never be able to escape and grow.
Their plan, however, was being reported to the dragon by one of their own. The loyal second king, a mantis shrimp explosive and powerful, told the dragon their plans. Swimming as fast as he could on the day the cavern had been completed, he ran and told the first king.
The first king and the first king's brother. The oldest sea dragon, and king of their kind. The kingdom, and the title they gave the king, the humans called All for One.
Seeking a swift victory, the old king All for One ate all the rulers bar one, taking a chunk out of his side and leaving him for dead, going to mourn the death of his brother in peace. Taking the half-dead second king with him, placing him in a secluded village on the edge of his drop off kingdom. In his sadness, he fled to rest in the brine pools deep in the dark ocean. Ignoring for 50 years the Mer king he had let live.
He had ignored the declaration of the immediate execution of all Sea-Dragons, had slept through their exile and had dreamed of their bodies, laying with him. He ignored it all, until one day, awoken by a curious dream, he wanted to check on the second king and if he had survived.
He travelled to the village, taking pains to camouflage his tail and colour it out of its pale whiteness, and had entered the village. Being immediately set upon by two mer women, one heavy with child – who looked for too similar to the second king for Hisashi’s liking, and a beautiful green betta fish mer.
Falling in love, Hisashi thought, was much easier than he had thought. But the lonely sleep had called to him long before she told him of her own pregnancy. He slumbered through all the years, as the second king's grandson was born, and his own. Stirring slightly as his cries echoed through the water.
Rising to consciousness only once, when he thought he heard his brother crying to be saved from the darkness. Four years after he had fallen into a deep slumber.
He never truly slumbered again, half-awake trying to capture another glimpse that his brother was still alive.
Izuku swam through the dark. His long dark green tail fins fanning out behind him. The betta fish fins calmly float behind him in the water. The equally long and floaty fins on the side of his body, at the ends a deep green – like that of the kelp forest his mother came from, and near his tale a pale almost white green.
His tale, long and strong, was a stark white. Like his father's tale, or so it was said - he knew his mother and she couldn't have been the dragon, he didn't know his fathers. The lack of camouflage in the tail calls his heritage to the sea dragons of old. They were the biggest predators in the ocean, they were protectors and scions of the moon, and their young were fiercely protected. Nothing threatened them.
The dark cavern that he had been imprisoned in since his markings had revealed themselves was large enough for a fully grown sea dragon, was built to hold one, a culmination of six kings and queens coming together to hold one of their own. Even empty of markings or the story behind it, Izuku seemed to know what it was for. Whispers on the tide told him, told him to wait, he would be free soon.
When the darkness grew heavy and scary, Izuku would lay at the bottom of the cave. Where there were small holes to let in the tide and the smallest of fish in, and listen to the whispering of the ocean. It had become too painful in the last few years, he had become too sad to hear all he was missing.
Izuku had barely seen the moon since the colour in the scales of his tail had come in, was barely a baby in terms of sea dragon, yet was held in the prison for one the size of centuries. Even if he was a half-ling, he would age as if he could eat and swim he would live for as long as he wanted. Far longer than humans, even far longer than the ageing of the Mer’s. Their own life spans doubling, or even tripling that of the humans.
Flipping over in a languid movement, Izuku made his way to his cave, situated near the holes in the floor, an anomaly in the circular prison. Just big enough for a nest, but just smaller enough for him to be safe in it. Brushing his hand against the kelp at the bottom of his cavern, he went and curled up in his little nest, the little colony of luminescent algae that he was growing was situated there. Having floated in from one of the underfloor vents.
It was the only place he could see anything, other than when King Yagi came and saw him when he changed into his mortal shape and walked to the lip above the water. When he came and saw the dragon pup in the cave he helped create it for the pup's uncle.
Izuku didn’t know how long it had been since he had been thrown in there, his small body striking the water in the darkness and his frantic swimming as no opening to leave out of was revealed to him. Being ripped from his mother’s body by the king's men and torn from the simple life at the edge of the reef and thrown into the dark, had been a hard adjustment. Most of the time he was here he was alone and in the dark.
Izuku often wondered how Kacchan was doing and if he was in the royal guard yet, the mermaid had often waxed lyrically about how he would be the best guard and would guard the king himself one day. He would be the best warrior in the whole realm. Especially with his ability to boil an enemy with his mantis shrimp tail.
Laying down in the soft down of the kelp that he had carefully woven together to craft a soft bed Izuku curled around his tail, playing with the membrane of his fins softly creating jelly-like shapes in the water. The green and white in the tail glowed in the soft blueish white light.
Despite all that it had hurt him he could never hate the colours in his tail, the fins were so intricately decorated and shining in so many different colours that Izuku took hours to stare at them.
Kacchan had nice colours in his tail too.
A small skrill passed by him carefully, its small body darting this way and that in the light. Izuku thought that he would have to move some of the luminescence colony soon, to draw away some of the small bug fish that he found everywhere in his nest.
Sighing, Izuku decided to watch the skrill as it swam around his head, the small currents that allowed fresh water and small creatures to enter his prison, causing the little fish to sway in the dark. Blowing it close enough to him that it smacked into his face, right into the centre of his forehead.
A small apologetic mental tug alerted him to the side of his heritage that he most loved, and longed to see more of. Sea dragons, the original inhabitors of the ocean before the mer kingdom of Atlantis sunk into the waves and became the mer kingdom, could communicate with their fish subjects. Even if most of them could only communicate with mental nudges and small hints of words since most fish did not think with anything other than mental images.
Often begging, often crying, often a fish screaming not to be eaten. Or so the old tale said, the salt wives' tales to turn children against the wonders of what sea dragons could do.
Kacchan one said that it was obvious that he himself was a sea dragon because only they were good enough at fishing and hunting as he was that he had to be. Even though the colours in his tails were vibrant and beautiful, it was shrimp shaped.
Shaking his head to get the thoughts of his old friend out of his head, Izuku watched the small fish – already having forgotten about hitting the scion of the ancient dragon king – float out of his nest and towards one of the holes in the walls, in jealousy as it floated out in its freedom.
Sighing he laid down and snuggled into the kelp, it had been so long in the dark that Izuku could only sleep when he wanted to. There was no light down here, and no way to tell when the moon was up. It was through some inane ability that he could tell the passing of the months, each full and empty moon had weighed on his body and mind.
Crying out to see him, the old relationship between the sea and the moon was what birthed the dragons. If you wanted a sea dragon docile, keep them out of the light of the moon. Just like how land dragons needed the fire of the sun to soak in to fire up their internal furnaces. The sea dragons needed their mother's eye on them to help her move the tide.
Nuzzling deeper into the green of his bed, the smaller cave that had been carved into the rock protecting him from nothing, Izuku let himself drift off into the dark of rest.
Something large shook the water around him, but the darkness was so absolute that he could not see what was near him.
Izuku could only hear the minute splashing of his own fins in the water, the long flag like fins that came from his sides and the end of his tail trailing behind and wrapping around him as he spun in panic. Trying desperately to catch sight of the large thing that was slowly whirlpooling around him.
A dark laugh echoed around him. The snapping of teeth vibrating through his skull, squeaking in fear Izuku froze as he felt large eyes on him.
A sense of claustrophobia pounded into him as the water around him packed into him, he could just sense the large clawed hands caging him in. Moving him closer and closer to the maws of the giant beast that had him trapped.
“Where did you get too little one? Why can’t I find you?”
The voice was tender, in contrast to the fear and anger that was surrounding him, it sounded loving and had a note of longing in it.
“The mother moon hasn’t seen you for many of her turns, her brother sun has also noted your disappearance. Where are you little one? Tell me and I will come and get you. Tell me little one, and we will swim in the depths together. Nowhere in this dark ocean can they hide you from me. No king, nor serf will keep you from me.”
The hands open and light had replaced the dark, a large white snout filled his vision and red orbs were boring into his own green eyes. Suddenly, the water seemed as if it were shifting before his eyes, a wavering mirage before the large dragon before him was replaced with a large mermaid. As large as the king.
A large mermaid with a large whitetail. The large fins off of his sides like his own were flowing and long. Just like his own.
“Where do they have you Izuku?” the mer said crowding into his face, his hands cupping Izuku’s face tenderly, “the smallfolk say you are in the dark, they say you are imprisoned deep where the moon can’t get to you. Where do they have you, little one.”
Izuku welled up at the tender care he was being shown, tears spilling over his eyes as his mouth failed to produce any sounds, opening and closing as the light around him faded, the man in front of him fading too. His voice warped as his vision tunnelled.
“Don’t strain your self little one. I am coming for you. The moon is in our hearts, my little one. ”
Izuku woke in his kelp bed, shaking his head and moving his tail to propel himself from his little nest. Dreams faded to the back of his mind. Wiping the crust from his eyes he danced in the dark of his cave, crooning in loneliness.
They would feed him soon, in Izuku's estimations, and he needed to be awake for when the fresh alive fish are tipped into his dark cavern, they came what Izuku could only guess was weekly, and if he hunted them before they came with more he wouldn’t be eating. He had finished the last fish yesterday from the last feeding, they didn’t last long in the dark as he did.
As if summoned, Izuku heard a grinding noise, echoing around his cavern and moving him to breach the surface at the top of the water level, his head above the water and nothing else. Still far from the lip where most of the other mer’s and humans walk, but still close enough that they would be able to speak to each other.
Flooding with light two human servants swooped into the walkway, replacing and lighting the torches on the wall. His tail twitched with impatience, he wanted his fish, he didn’t need the light and the headache that was building from the harsh light made his own temper build.
It was tempered slightly when the king swoop in with a cheery hello. Izuku responding with his own chirped hello, accompanied with an impatient, hungry, noise that sent the king into a rumbling laugh.
“Here we go Izuku, it's been a while hasn’t it.” The king said sitting on the edge of the walkway, his feet not dangling even close to the water. Izuku was sure that he would be able to grab him if he got the momentum from the bottom of his cave.
“Yes king, you have been away for a long time.” His own voice croaky with misuse. “What fish do you bring me today? Which do I hunt in the dark?”
Sharp teeth enunciating the words as sweat drops down the king's neck. Yagi Toshinori was always torn between feeling sorry for the young merdragon pup in the dark cavern, but then those large teeth glint in the firelight and the wound on his sideburns. They always sent guilt inside him as well, but he buried that deeper than the pain.
“My guards are just bringing them, my boy, I have good news as well.” Toshinori said, forcing himself to be calm, “I have a new guard as well! He replaced old Aizawa, now don’t give me that look I know you liked him. He wanted to be moved to guard you here, so don’t worry you still get to see him. Ah young Bakugou you’re here! Come meet Izuku.”
Toshinori heard the trill of excitement at the name, ignoring it and focusing on the two men and the bucket between them. The sound of excited slashing echoed all around the chamber before a name cut through the quiet.
“KACCHAN!”
The bucket slipped out of Bakugou’s hand, and Toshinori surveyed his face as deep shock and something else glanced through. The fish, desperate to be in the water and flopped into the pool. Izuku, as opposed to his normal behaviour, ignored them taking to staring at his new guard.
“Kacchan? Is that you kacchan? Has Kacchan come to save me?”
A wounded sounding noise escaped from the young Mer, before he fell to his knees whispering a soft, “Deku?”
Ignoring the warning look from the king he spoke again, “fuck Deku is this where you’ve been for the whole time? Is- is auntie Inko with you?”
Toshinori decided that it was time to get the boy out of the room, it had been an unfortunate thing – to kill that young green Betta fish – but given the circumstances it was necessary. Not that the child knew that, well not a child anymore, looking at the Mer at his feet. If he had been allowed into the wide open ocean he would have been the same age, but the cramped living quarters and the moon not gracing him with its magic had kept the pup small, kept him barely a child.
“Thank you young Bakugou, please wait outside with Aizawa. Yamada and I can handle this.” The explosive blond didn’t move for a few moments, he was incredibly still almost prostrate before the king, but the movement of his head when he turned to look at Toshinori exploded a sense of recognition in his mind. The second king had given him many looks like that.
“No, I want to fucking know why De- Izuku Midoriya is being kept in a dark” he sniffed deeply as if to prove a point, “manky fucking cavern, and you want me to just walk away? Where is Inko Midoriya? What did he do to deserve to live here?”
Katsuki had scrambled to a stand facing, stubborn but so young.
The kings face went sharp as his great white shark characteristics came to the front, his teeth sharpening, “Bakugou out. We will be talking about this later. You will not question me, this is a matter of the safety of our kingdom. I said OUT!”
Bowing lowly, low enough that only Izuku could see his jaws that had clamped together, he caught Izuku’s eyes for a few moments. Enough for Izuku to smile encouragingly, to tell him that it was ok. Katsuki grimaced as he stood up, stony-faced he turned, with one last look at Izuku before storming out of the room.
It was enough excitement that Izuku ignored the fish that were languidly swimming around him, the soothing murmurs of their minds quiet enough that Izuku ignored them completely to keep his sharp eyes on the lip of the cave.
“Excuse Kacchan, his temper had always been explosive. Where is my mother?” Izuku asked, his eyes wide and seeming to swallow all the light in the room, the sweat on Yagi’s neck grew cold. The question so sudden, after years of pleasantries, Yagi was once again unnerved by the uncanny way the boy reminded him of the first King, “When am I allowed out? Your highness, I have been here for a very long, and you still haven’t told me why I am here. When can I swim in the ocean?”
The king looked at him from the ledge of the sandstone cave, rings of sediment forming a sort of centric circle around the two, he had had it designed like that. Staring up at the mer King Izuku knew that his question, again asked with a bluntness that seemed foreign to a child, would never have been answered. The king opened his mouth, but with a smile, Izuku cut him off.
“Don’t worry your highness, I don’t mind it here, its my own little kingdom. The moon is in our hearts, good ruling King Yagi.” He slipped back into the water with a soft splash, his tail breaching the surface and showing off his tail spines and fins. A show of his heritage, despite not understanding it.
Humming to himself the king withdrew, he would need to talk to that guard. Bakugou was a strong, powerful and useful tool. But this was something he needed to nip in the bud.
King Yagi never saw Bakugou again.
Nor did he even think of why that saying sounded familiar.
Izuku was sleeping when he felt it. Felt the walls of his prison start to sunder under large claws. The ripples around him shook him unsteadily.
The door above him burst open, guards spilling in behind the king. Large nets bundled in their arms, waiting to be cast into the dark.
Unsure of the men who came in, yet scared of the desperate scratching and deep growls that permeated the water at the bottom of his cavern, Izuku hovered in the centre of the pool. Watching through the water as the king tried to call him to the surface and as he got more and more impatient, watching the guards cast the net. Izuku moved closer to the bottom of his cave.
Whatever that creature was, he was a sea dragon, the tales all agreed that no one ate sea-dragon pups.
More and more of the nets were thrown into the water, casting to tangle him up in their rope. The muffled sounds of shouting and anger barely came to Izuku, the calm of his ocean habitat only offset by the sound of a large creature fighting.
Then someone dived into his pool. No one had come into his pool before.
A mermaid with the lower half of the orca started to crowd him towards the side, his large spear and even larger teeth and claws intimidating the child to cower against the sides. Another splash and Aizawa came up behind the mer, the catfish mer shouldering the larger out of the way as the sight of someone familiar soothed Izuku.
Isolation had made him wary of strangers.
Aizawa, trying to calm him down, was holding his arms out in a placating gesture, speaking slowly in tounges that Izuku had forgotten from only hearing human voices, and taking his attention away from the orca. The moment Izuku drifted away from the wall, the sounds of fighting faded slightly as if the creature had moved away, which was when the Orca struck.
Throwing his spear he pinned Izuku’s tail fins to the wall, the point sinking deeply into the rock, through the delicate membrane. Izuku cried out, missing him rushing forward, and missing the net he threw Izuku, and none too gently tearing his spear out of the wall and the boy's tail.
Tangled and bleeding Izuku thrashed at the feeling of the rope on his skin, at how his delicate fin membranes tore and were restrained. Of being dragged to the surface as the Orca tied the net he was into rope that was used to pull Izuku out of the water. Ropes in the shape of ladders were thrown into the pool for the two mers who were still in the pool. Aizawa looked as if he would attack the Orca as he climbed out.
Izuku’s thrashing increased as he was dumped onto the sandstone ledge, he tried wiggling to get to the water of his pool. He missed the darkness and the cool warmth of the water, something was dripping onto his face as he was heaved over someone's shoulder his own breath growing short as he was taken away from the water.
He was heaving his own tears as they went through the doors, he missed the darkness. He couldn’t get enough air in! Flopping on the Mers shoulder, he couldn’t move his hands to claw at his throat. Limply thrashing in the net was all he could do.
“We need to put him in the water! Yagi, your highness, dragons don’t have a human form! Your highness, he will die!” Aizawa cried from somewhere in front of the man who was carrying him. Hanging limply in his grip as he struggled to keep his breath. The voices around him turned garbled as the loss of oxygen got to his brain.
Turning around a corner of the human palace he had been brought through, a large crash echoed from behind them, the door blowing off as the water rose to smash through the hallway. Flooding to their knees before slinking backwards. Spraying the walls with seafoam and bits of seaweed. Izuku thought he saw something impossibly large, a large red eye framed in white before they turned the corridor completely. The party sped up in their haste to escape.
Izuku lost consciousness soon after.
Aware of only a few moments, the suffocating staleness of a small tank of water. The heat and dryness of the sun, his arms chained above his head and the top of his body out of the water, and then nothing.
Waking only later, laying – once again – on the soft down of kelp. Sighing in the darkness, it had only been a dream, Izuku lazily started swimming to the main part of his cage, his internal compass moving him to the door. Sighing in a small show of happiness, the luminescent algae had moved by itself.
He hit something warm and scaly in a matter of moments. A rumbling grumble accompanied his movements as he sped backwards, to distance himself from the large thing in front of him. He hit it again, his back flush against the warmth once more, it had only been a few strokes of his tail, had they put him somewhere smaller?.
In a panic Izuku kicked his tail, trying to at least see if this warm cave had a roof. It was the same thing again. Striking against the warm rock he shuddered backwards when he suddenly felt it move. As if it were a large serpent uncoiling itself from around him.
Because apparently, that was exactly what it was. A large serpentine sea dragon, white in colouring, red eyes, and large – so large – with a thin and snake-like tail unfurled from around him, the very end circled around him as if he were protecting him. Izuku recognised this dragon, the dream he had, this was the dragon.
The water was a silvery tone in the semi-darkness, and Izuku turned away from the large creature that had been staring at him to look at the thing that was shining at him through the water.
The sea dragon known as All for One followed his hatchling gaze to the moon and watched with him.
“What did I say little one? The moon is always in our hearts. Welcome to the ocean, hatchling.”