Riordan owns this franchise.
Black Trident.
Chaos bless the Prince of Sea and Night
This was a joyous, triumphant date for Atlantis considering the monarchist nature of everything divine. Their Lord had recently returned, with his immortality and status as an Olympian restored.
Furthermore after the fallout of Atlantis' previous royal couple with Amphitrite's subsequent departure and breaking of her marriage, sanctioned by Queen Hera herself, the morale of the people rocketed almost to the surface when Poseidon returned with a bundle in his arms. A small child with midnight blue eyes and the darkest strands of hair growing from his little head.
Atlantis had a new prince, the seas embraced the child like a cradle, he was indeed one of the Ocean's own. But not only did Poseidon's domain claim him as one of theirs. No, the dark abysses of the deep also called for the godly child. Many of young Perseus' caretakers were initially distressed and even afraid about this baby and his aura of shadow. Some in Poseidon's court even raised an alarm about a possible attempt on their prince's life by an Olympian or Titanic threat that they weren't certain of, but the Sea God put their concerns down by assuring they had nothing to fear about or for Perseus.
Nevertheless, questions were being asked by the always loyal people of the sea, they wouldn't dare to accuse their Lord of treason but curiosity remained. After all, it was rumored that not even the Atlantean High-command or the Oceanid sages or even prince Triton knew the truth about what went down during Poseidon's exile and revoking of godhood.
Mermen spies on Olympus informed the powerful circles and Prince Triton (at the time acting Lord of Atlantis) about Poseidon entering Tartarus a couple of years ago as a demigod. Well, fast forward to the end of his punishment and the bastard showed up at the gates of his abalone palace with a full-blooded god child in his arms.
Perseus, as he was named by his father, quickly dissipated all doubts about his lineage (as if the pressure of the depths not hurting him and his natural underwater breathing wasn't enough) he managed to understand horses even before he understood people. Before the baby even managed to call Poseidon 'Dadda' he was seen several times eyeing the hippocampuses like an attentive cat when they whinnied and neighed, and the Atlanteans who understood both heard the creatures having semi- one-sided conversations with the prince. He was Barnacle beards' spawn, no doubt.
But that still left out the why of the immense power he radiated, the way shadows and darkness seemed to bend to his playful movements, and even physically, Why midnight blue and not Sea-green irises in his eyes? All of Poseidon's kids inherit his aquamarine eyes, but not this one.
Well the answer to all of those questions slapped the people of the sea across the face like a cold fish when The Fates showed themselves in Atlantis and requested a formal audience with Poseidon and his court, to make matters worse for the people yearning for truth, they sadistically teased that they were there to discuss the youngest son of the Olympian Sea god.
When the councils, nobles and army chiefs of staff assembled in the Royal Palace the fates bowed only to Poseidon and just by the fact that they were in his domain uninvited, much to the chagrin of the rest of the court.
"Greetings Lord Poseidon, it is always an interesting experience to come down here to Atlantis." Clotho opened
"Yeah yeah, save the diplomatic ass-kissing for Olympus, we know everything's in your hands and that we shouldn't or couldn't try to change destiny, we know. Now onto the matters of my brother if we can." Prince Triton replied before Poseidon could, riskilly displaying the all too traditional haughtiness and snarky rebellion of all the sea's own.
The Olympians would be flabbergasted by this utter insolence, but no one here was really surprised, children of the sea are sarcastic punks pretty much by factory settings.
"Very well, let's get down to business." Lachesis picked up the ball and started rolling the discussion
"Yes, most immortals, with all their stubbornness and pride know their fate hangs by whatever thread we want to pull. But we do have a mother you know, she sent us here in fact." Atropos continued making Poseidon's eyes widen, his expression showed both surprise and joy.
"Why is this even a dramatic revelation at all, the big three brothers have basically wiretapped each other yet no one bothered to listen to what happens in Tartarus." The alotter groaned
"Regardless, with all the Hellhounds yapping excitedly about this it's only a matter of time Hades finds out, and upon mother's instruction we come here to officially claim Perseus as a blood child of the night, first to Atlantis then to Olympus."
The palace was engulfed in silence.
"My lord, I mean no insubordination or disrespect, but what the fucking fuck?" Delfin asked first and soon a cacophony of stunned gibberish filled the court as the revelation that Perseus was a half-primordial son of Nyx.
"AT EASE EVERYONE." Poseidon finally ordered his people.
"It is true, my youngest is a son of Nyx and I, he's the product of our love, conceived when my godhood was returned."
"F-father?" Triton inquired
"I am so very sorry son, I failed your mother and you in a disgusting manner, I daresay I was even worse than my manchild of a younger brother at one point. When Amphitrite declared she was leaving it felt as if Atlas had relayed his burden to me, and I felt the pain of my own sins right there. But I don't regret or resent little Percy for anything.
"I am so sorry for driving your mother away, but know that I will not fail you again, And I'll be damned by the fucking Styx if it's not like that. Nyx saved me, her healing of me was my actual salvation, not the restoration of my ichor. The house of night was no torture, it was repentance, and Nyx still showed me compassion and a reason to change, better said another reason, because learning how much of a swine I was make me accept that you, my son are a reason to actually be loyal to my own.
"Mark my words Atlantis, witness this Lady Fates. From here on out, the sea will NEVER betray or forget its own."
Triton was so taken aback by his father's proclamation he almost dropped to his knees, this was all he had wanted to hear his whole life, he had learnt to not be spiteful towards the bastard children of his father like Hera, but that did not mean that he was tolerant to him breaking his mother's heart bit by bit.
And one would be forgiven if they assumed that upon learning that Perseus, or Percy like Poseidon called him, was his newest LEGITIMATE children, not even half a century after Amphitrite left Atlantis, Triton would gut him then and there.
But he did not, Poseidon's words made every ill thought about Percy wither away, if he was truthful, which he most likely was since proclaiming in front of his people, the fates themselves and taunting the Lady Styx would be too bold even for the boldest god, which of course he is.
But he did not swear on her though a thought quickly made its way towards his mind-
-and was again invalidated by the sudden apparition of Lady Styx in her carnal form. A beautiful, mildly pale woman, hugged by a black dress and a necklace consisting of miniature figures like a Macedonian helmet, Icarus' wings and other hopes lost to the circumstances and probabilities that hit human lives.
She said nothing about this being the first time she ever left the underworld for somewhere that wasn't the Olympian throne room, instead she looked at Poseidon dead in the eye and raised her eyebrow.
"Really. I get to damn you for eternity? You, the most upstart prick among the divines, are swearing off to never do something? Please, that is a speedrun to you doing it."
Half the presents were thrown off their shock, which was replaced by rage and swords being unsheathed and drawn towards the oath river goddess that just talked shit about their Lord in his and their faces.
Poseidon raised an open hand "Stand down, she's right. But I have to make this oath."
Styx's other brow raised "Well… swear it."
"..."
"Do it."
"…"
"You cannot do it right? Old tricks aren't ditched easily after all. I'll take my leave no-"
"No, don't. Please." The god interrupted pleadingly and gave a sigh . "It must be done. The sea is erratic, free and unpredictable, but when I already crafted the fame for myself that if I'm told not to do something I will do it I must reconsider my ways. My nature yearns for freedom and power, but I can no longer make the most of freedom and of pleasure without my family."
"For the honor of the Sea, for Nyx, for Triton and for Perseus I swear on the river Styx to never betray or forget my family and my people. If it weren't to be that way, let Atlantis hold me accountable and Lady Styx to damn my soul for eternity."
To this final proclamation even the three sisters of fate gasped astonishedly. Styx narrowed her eyes but when, not a thunder but a rumble coming from the tectonic plates sealed Poseidon's oath she couldn't say anything more against it.
"Very well, I will be watching even closer than I did before Poseidon. Congratulations on the brat."
And just like that, the Oathkeeper was gone.
"Ahem" Clotho made the court reacknowledge their presence "Well, now that that's covered, Lord Poseidon, can you please summon young Perseus?"
The sea deity nodded and disappeared in a flash of bubbles to reappear with Percy wrapped in a sea green blankie.
Lachesis held Perseus for a brief moment until all three of the sisters simultaneously chanted.
"ALL HAIL PERSEUS, GOD OF MARINE TRENCHES AND ABYSSES, PRESSURE, DEPTHS, LOYALTY AND SUBMARINE SAILING."
The Atlanteans cheered and knelt to the infant god and their prince as Poseidon and Triton smiled the warmest smiles.
Atropos went into specifics "His sacred animal will be the Killer whale, playful and loyal but extremely dangerous and battle-smart. His symbol of power will be a Trident like his father and brother, but his will be specifically black-colored. And he might gain more domains as mortals advance their exploration and understanding of your realm."
The news was already starting to spread through Atlantis when a black flash appeared in the middle of the courtroom stopping the last of the euphoric people who were halfway out the threshold. When they turned to see what was happening every single soul present lest Poseidon and the Fate sister had the deepest gasp in their entire lives.
Here she was, in all her magnificence and beauty. Nyx, Goddess of the night. An extremely beautiful, almost unbelievably stunning woman of fair skin and raven black hair that secreted an aura of power (and a look of being able to easily smack you like a bug) was here.
Normally, waltzing yourself into a god's domain, one of the big three and in their palace at that, would result in blood spilled. Even if the 'assailant' was indeed more powerful, very much like now, the three eldest sons of Kronos are far too proud and stubborn to let it slide and would most likely defy even Chaos to achieve the least orthodox suicide method, perhaps only Hades would be able to maintain composure.
But Zeus and most definitely Poseidon would not bow.
No, instead Poseidon is… grinning like an idiot.
"Nyx! You're here!"
"But of course I am barnacle brain, how would I miss Percy's officially being recognized by my daughters. Oh and I guess also seeing you is a thing." She faked apathy for the latter, making the sea god pout his lips and grumble.
"...well you just missed it woman."
"Eh, the night arrives a minute late or a minute early, but she always arrives. Now let me see my little shadow." She smiled, warmly now.
Poseidon handed the bundle to his excited lover whose smile widened and her eyes gleamed with affection.
"He's beautiful, son of night and sea…" As the Primordial goddess mused she placed her finger in Percy's little left wrist and a mark showed itself. A beautiful Obsidian colored trident manifested in his skin.
"Son of night eh? How about that Triton, reckon he'll become more of our little brother than yours?" Clotho taunted the heir of Atlantis, whose smile broke and he glared back, now completely protective of the little shrimp his brother was.
"Keep dreaming Moira, he'll be a fine son of the sea and give honor and pride to us, maybe even redeem our kingdom and make the Olympians eat shit." He clapped back albeit with a non-hostile tone, they were technically family now
"Chaos be with you young Perseus." Atropos wished her half brother, with that ending the ceremony and the group dispersing to celebrate how they saw fit.
Unbeknownst to them, the news wouldn't be late to arrive to Olympus and Hades, both of whom started to ponder about how to play their next moves.
I intend to develop Olympus, Atlantis and the Underworld's politics in later chapters, and eventually make a prequel about trial-mortal Poseidon making it through the house of night so this isn't a massive asspull in the end.