Percy loved fighting underwater. It was like how he imagined Jason felt in battle, lunging and dodging and spinning smoothly a foot above uneven dirt, pockmarked with crests and divots; the son of Jupiter always had the high ground, courtesy of being able to step on the air itself. Hundreds of yards beneath the lake's surface, Percy felt the same. Never did his feet step too far or too little as he swung at Triton, never did he slip or stumble. When his skills fell short against thousands of years of experience, his half-brother's trident suddenly found itself jabbing at empty water when Percy willed a current to carry him out of harm's way.

Not that he could claim to have won most of the duels- those he had claimed he stole with trickery and well-laid traps. However natural it felt for him to spar beneath the waves, it must have been tenfold for Triton. Dueling against Jason aboard the Argo II had helped prepare him against an enemy that could attack from all angles, but legs couldn't compete against the god's twin fishtails underwater. Triton had been born for the sea, even more than Percy was.

Look, he didn't want to be jealous. He'd given it his best effort, but after five days split between Aberkios metaphorically beating history and law into his head and Triton literally beating a trident into his head, he'd admitted to himself that there was envy burning in him, hot and furious and consuming.

Triton had never found himself at the mercy of a prophecy. Triton had been raised by both his mother and father. Triton had married the love of his life. It isn't fair, he'd thought bitterly. Sometimes he wanted to let loose and push himself to the limit and see how much misery his spoiled half-brother could take. He didn't, though; the training yard was no place to lose control. In the absence of vigilance stalked misfortune.

Percy had known, abstractly, that Triton had fathered Pallas, and that she had fallen to Athena while sparring, the daughter of the sea distracted by Zeus taking the guise of a golden eagle. Sunlight had glittered off the god's wings and blinded Pallas before Athena's spear pierced her side.

It had not been an easy death.

Triton's daughter had succumbed to blood loss, godhood yet to fully gild her veins. While Percy didn't have to worry about accidentally killing his half-brother, Percy still bled red. Late at night, when the inner dome had quietened and the mers rested save for the sentries on watch, on days he escaped injury in yard, he checked to make sure. Just a small cut, barely enough for a drop to escape into the pleasantly cool waters of the lake. The sight of crimson welling up was worth the pinprick of pain.

The glinting of Triton's net broke him from his distracted defense, sending him rolling to the side before kicking upright again to catch the blunt end of the trident with Riptide inches from his head. With a growl, he pushed it way and flung himself forward, sword outstretched. It was aggressive, overly so- Triton was already retaking his neutral stance by the time Percy lunged. The god could move out of the way with a single flick of his shimmering green tails, scales looking like emeralds in the light of the leyline's power that ran straight above them.

While Percy passed by harmlessly, Triton would have his pick of points to jab at. Painful, but not quite bad enough to require medical attention. Wouldn't want the half-blood taking a vacation in the infirmary, Percy thought sardonically. Better keep him in just good enough shape that he can be stabbed again. Triton seemed to enjoy stabbing him.

It was a bit concerning, but Percy was rather counting on it as he soared through the water, catching a look of predatory glee on his half-brother's green-skinned face. While twisting the handle of his trident upwards, preparing to push it down at a 45-degree angle into Percy's side, Triton froze, arm pulled too far back to defend himself.

Father turning away, flicking his hand up sharply in dismissal; a young, green merwoman in pearl-studded armor in his arms, surrounded by a coppery haze; a limp, coral colored hand reaching out from beneath a massive brick resting on the sea floor, with a familiar spear on its palm.

The moment of distraction was all Percy needed to kick Triton in the head, causing the god to move once more, snarling and cursing as Percy used his momentum to pivot and hold the edge of Riptide against Triton's nape. His pitch-black eyes darted to the celestial bronze length before latching onto Percy's face, glaring murderously.

Sorry dude, but misery is, by definition, kind of miserable, the demigod thought as he let his sword drop down to his side. Still, Poseidon had commanded Percy to practice, with Triton and Kymopoleia acting as test dummies. It wasn't exactly a party for Percy, either. These test dummies hit back, after all, and did so with godly strength. Besides, whenever he used his powers, he felt every ounce of misery he inflicted, even if there was a strange surge of… something that accompanied it. Whatever it was broke his heart even as it quickened in anticipation of more.

It sickened him.

He held out his hand to Triton. "Good spar," he said with a forced, easy grin.

"Nice handicap," Triton replied, sneering, compelling the water to force Percy's hand back down to his side. That was a bit rude. Not surprising, but still rude.

"Nobody said you couldn't use your powers," said Percy. There was a storm brewing in his gut, countless minor offenses swirling together to create something greater and worse than the sum of their parts, like soldiers forming a phalanx.

The messenger god of the sea smiled. It was cruel, and condescending. "I could crush you like a minnow in a shark's maw, but I've been told to you keep you alive."

You know what? Screw you. For days Percy had put up with this crap. "Big talk. What are you going to do, send me a strongly worded letter? Hit me with a cease and desist?"

"Mind your tone, boy."

"Sorry, you'll have to mail in the proper forms for that. I can give you couple stamps if you need them, though." He might do that anyways just to see the look on the god's face.

Triton sniffed dismissively and turned away. "I've better things to do than humor an impertinent brat."

"Maybe if you train really hard, you'll be able to fight the god that impertinent brat faced at twelve without that same impertinent brat helping you," Percy mockingly encouraged.

Yeah, Triton was doing pretty alright last time, and Ares wasn't going all out when I first fought him, and then there was the thing with Kronos, but eh, semantics. Wait, did I just call myself a brat? His words were enough to make Triton whip back around, ebony eyes glowing, as though wreathed in living shadow. Pretty sure light isn't supposed to be black like that. A pause. I hate that it kind of looks cool. Like mascara, but 3D. Percy was mostly certain mascara was the right term, but he'd only been half listening to Piper's rant, so he could be wrong.

"If you have a death wish, perhaps you should have indulged it before you forced father into a war. Still," continued Triton cruelly, "It's not too late to make everyone's lives easier."

Percy could have taken the high road and ended it there. Clearly, his half-brother had no chill, and it would be best to avoid this escalating. They were, after all, on the same side. He could have swallowed his indignation and vitriol, bitter as it was, and let his boiling blood cool off in the depths of the lake. Then Triton opened his big mouth again.

"Maybe that owl spawn will even forgive you. I doubt it, though."

Percy saw red. "I'll make sure to say 'Hi' to my niece while I'm down there."

The instant he said it, he regretted it. (Did he?) There'd been an unspoken rule while he and Triton and Kymopoleia had trained that Percy would never speak of what he saw when Misery swept over them. Even without it, he knew he'd crossed a line. (That his half-brother had swam past first.) For a moment there was silence, broken only by distant noises: the clanging of the forge, the swirling currents set in motion by hundreds of mermen, and the faint humming of the leyline. Then Triton charged, roaring.

Around Percy, the water hardened and collapsed, set to crush him like it had wanted to from the moment he'd stepped foot into the lake. There was a sense of glee emanating from the waters of the deep as they bore down on him. I'm going to dump so much sand into the Mariana Trench that it'll be called the Mariana Speed Bump. It took every ounce of willpower to hold it at bay, dropping to his knees as Triton raced towards him, twin tails churning the water. He pushed it away and rolled to the side, snapping a long stream of it like a whip at the approaching god, who blocked it easily with his trident before redoubling his efforts to flatten Percy like a tin can.

Don't challenge sea gods when underwater. Duly noted. I probably should've already known that. Then Triton was upon him, and Percy's internal monologue was interrupted by a glittering celestial bronze net coming his way. He pulled at the water this time, letting it carry the net over his head.

Percy blocked a trident thrust by slicing upwards, flowing smoothly into a downwards slash that Triton avoided, propelling himself backwards with a flick of his tails. They traded blow for blow, and the half-blood found himself being forced back by divine strength. His retreat was (mostly) controlled, right up until the god summoned the net back to him, wrapping around Percy like a cloak.

As swift Triton raised his trident, Percy called forth Misery…

A raging Amphitrite, poking hard at his chest as she shouted at him, tears streaming down her face; the North wall of Atlantis falling, sending up a fog of sand that wasn't thick enough to hide the soldiers that fell with it; a teal-skinned merman being ripped in half by two tentacles of a massive kraken even as the others reached for him; a shroud, embroidered with a conch shell below a clownfish, bordered in gold and silver waves.

…and Poison.

Plants sprouted from the lakebed: water hemlock with bundles of small, white flowers; a bush with a dozen pale green stalks that broke off before sprouting two more in its place, which broke and split again and again while dripping a glowing green liquid; innocent yellow blossoms, the cursed mustard that caused Kronos such pain and nausea that he vomited out his children in a wave of bile; oleander, pale pink, beautiful yet deadly, coiling around motionless Triton's ankles and shins in a twisted semblance of affection. Around them, the water turned wine-red, dark and threatening, before it floated up to surround the god, forming a cage of toxins.

Percy gritted his teeth, straining to hold Misery and Poison and place, and peeled the net off to dolphin kick over to Triton, taking the trident from him almost gently. With a wave of his hand, still holding the fishing net, he released the flowers and the memories, water once again turning clear as both sons of Poseidon bent over, gasping. Delving into his domains without the might of leyline backing him was exhausting.

It took a good few breaths for both of them to straighten up, the half-blood coolly met Tritons murderous glare. In the depths of blazing onyx eyes, Percy saw traces of fear. Good, he thought briefly, before finding himself horrified. He held out the trident and net, which Triton took wordlessly.

As the god silently swam away, Percy wondered if the Sea accepted Poseidon because his father was akin to it, or if the Sea wore him down after he took it, eroding the god until all that remained was a reflection of itself. Not that Percy had been blessed with a choice; his lot had been cast without his knowledge, unwanted winnings accepted in ignorance.

It was a tad too late for him to give it back to Akhlys, though. The goddess was lost to Chaos, and She Who Is All was not like to return what was gifted to Her. Neither was Percy willing to journey to The Void again. Looking at it had physically hurt, like it was so far beyond his comprehension that it took offense at the puny mortal daring to gaze upon it. Which was fair- if Percy had created a universe, he'd probably think the humans in it were a bit on the short side too. He hoped he'd be a bit less high-and-mighty about it, though.

"Son."

Percy blinked in surprise; it was hard to miss the arrival of someone as powerful as Poseidon. He faced his father, who looked… not angry? Alright, better than I was expecting. "Dad."

"We should talk," said Poseidon, gliding forward to rest a hand on his son's shoulder. "Come," he commanded, and Percy followed him out of the training grounds. His father led him through the throngs of bustling merpeople, colored green and blue and black and red, to the seastone temple-castle at the center of the inner dome. It stood proudly at the convergence of the beams of light running overhead in each cardinal direction and upwards, towards the sky.

They floated above the intricately detailed, uneven steps, carved to look and feel like the surface of the ocean with shallow ebbs and flows. Why do underwater buildings have steps? Seems like a bit of a waste. Probably the extra surface area to decorate. Yeah, that seems about par-for-the-divine-course. The first floor of the building was dominated by an obelisk tipped with a massive chunk of aquamarine, glowing brightly. It had depth to it, as though the gem was larger than it appeared at first glance, home to a swirling nebula of Ouranos's essence.

He grimaced at the sight of it; it reminded him of the pain and power of holding it, of being a living cornerstone, and the ache and relief of releasing it. Also, it made him face the fact that he'd wielded a primordial's seed, which was… disgusting. Percy would have chopped up the Sky for that (or at least made a good effort to) if Kronos hadn't gotten to him first. After a moment in which the merman guards at the entrance and on the second balcony made a swift exit, his father spoke again.

"Part of learning your domains is controlling them. Another, more important step, is ensuring they don't control you." His gaze was heavy, but not harsh.

"Using them feels different. Like…" Percy didn't have the words to describe it.

Poseidon seemed to understand anyways, the lures on his fishing hat jingling softly as he nodded. "You were born of the sea. It is in your blood as much as your mortality is. To wield it is to wield yourself; it is as natural as breathing."

"Exactly!" agreed Percy, running a hand through his black hair. "While Misery and Poison- it's like using a different sword. Even if it's perfectly balanced, I have to adjust, change my reach and footwork. It'll never be Riptide."

"A good blade," his father said approvingly. Not biased at all, I'm sure. Percy certainly wasn't. Riptide was just, objectively, the best sword. "Yet your domains are more a part of you than even Anaklusmos. Perhaps it is my fault," he mused. "They are not merely weapons for you to train and fight with, only to be set aside after. Think of them as newly discovered limbs."

"I think I'd rather have two extra arms. Or wings."

His father's face twisted in disgust. "Really? Wings? Tentacles would be far more useful. Very adaptable."

"Fair, but imagine how much you'd have to spend on lotion when out of water."

"You could probably get Aphrodite to give you a discount, even without buying it in bulk," Poseidon said, rubbing his bearded chin. "She does have some rather nice seaweed-based ones. Though that's not particularly relevant at the moment," he said while crossing his arms over his shirt. It was a fluorescent green, which clashed horribly with the orange clownfish and garibaldi swimming through the strands of dark kelp on it.

"Right. Sorry."

A wave of his father's hand dismissed his apology. "Much like growing tentacles-"

"Wings," Percy muttered rebelliously. It was quiet, almost inaudible, a faint spark beneath the noon sun, as rebellion so often began. Yeah, flying would be a no-go, but they'd look so cool.

Poseidon continued as though he spoken, "-acquiring a new domain comes with new feelings and abilities both. To change as a result is inevitable." Dam. "Yet they belong to you as much as you belong to them. The sea does not like to be restrained, but you must not discard self-discipline. While Misery loves company, you must choose who suffers carefully. The dose makes the Poison, so you must not be without moderation."

Percy nodded, eyes fixed on the seastone floor. It was aptly named; the pale, blue-green rock was speckled with white and grey, as though the ocean had been frozen and mined and laid out in carefully cut blocks beneath him. "I get it. I'll do better."

"I believe you," his father said, resting his hand on Percy's shoulder once more. "Sometimes, though, remorse is not enough. Discord has no place in our ranks, now least of all."

"I'll talk to Triton," Percy replied. "I owe him an apology."

"Good. Do so today; tomorrow, you leave to speak with Hecate."

With a grimace, Percy nodded. "About that… like, I know history and law are probably important," (it might be helpful to know which rules he was breaking as he did so) "but they don't really seem too helpful for negotiating. She joined the Crooked One because she wasn't getting recognition, but now she is, and I don't really know what I'm supposed to bargain with." I've even been paying attention to Aberkios, and he could put an insomniac in a coma. Just recalling the tutor's voice was making him sleepy.

Poseidon smiled. It was secretive, ominous, like the dark water of a trench that cloaked a sea serpent from view until it was too late to avoid its hungry, sharp-toothed maw.

Percy didn't like it.

"She won't ask for anything," his father assured him, plucking a verdant leaf, oval save where either end came to a point, from thin air (water), and holding it out to Percy. "Just give her this and promise that with our victory, Olympus will be better."

Percy didn't like that either.

He took the offered greenery anyways, waving it experimentally and examining it to see if it was actually something useful in disguise. It wasn't. "This is a leaf," he said skeptically. "What am I supposed to do with this?"

"You're supposed to give it to her and promise that with our victory, Olympus will be better," his father repeated slowly, as if explaining something to a child. "And yes, it is a leaf: laurel oak, to be precise."

I didn't ask what kind it was, and I understand perfectly, thank you very much. It just doesn't make any sense to me. Well, if Hecate isn't willing to join us in exchange for some foliage and vague promises, I'll magic up some plants for you. Let's see how you feel about poison ivy. That'll even count as training, right? Not that Percy would actually do so, but the thought of it was cathartic.

"Okay," Percy said at last, when it was clear no elaboration was forthcoming. "You got any other tips?"

Poseidon shrugged. "Mind your manners? Don't insult her?"

"Right," replied the half-blood with a nod. Pretend she's not a god. Unless she attacks, in which case treat her like an angry god that wants to kill you and try to kill her first. Just another Tuesday. "What are we asking her for- direct involvement or something more specific?"

"She will offer the aid we need unprompted," answered the god of sea with another fathomless smile.

Percy was starting to despise that particular facial expression. He also, for the first time in his life, felt sympathy for weather forecasters; if Poseidon's own son couldn't read the storm-bringer, how on earth were they supposed to? Didn't Hecate help Zeus bar dad from the continent by tying protections to the cornerstone? I feel like asking her to undo that so isn't restricted to just this leyline might be a good idea. This is really sounding kind of fishy. "Have you and Hecate already talked about this?" That'd explain why he's been saying her name all this time.

Poseidon shook his head, still wearing that same thrice-cursed grin. "I need not ask my foolish brother where lightning will strike when the scent and feel of ozone are apparent; neither need I ask where the Mist will hang when I know the direction and manner of its flow."

That clears up… absolutely nothing. There's no way he's not doing this on purpose. "Is keeping me in the dark at least going to be helpful? Or important somehow?"

"Perhaps," replied Poseidon with a chuckle. "The Carrier of the Torches does so enjoy lighting the way. Be assured that, at worst, it will not hinder you. Probably," his father finished, shrugging.

Percy sighed. If this what talking to me is like, no wonder so many things have tried to kill me. I can't be this bad, though. I hope. "Alright. Is there anything else?"

The god of the Sea shook his head. "No. You're dismissed." When Percy turned to leave, his father spoke once more. "You will find my heir above the outer dome."

As he swam out of the temple, the familiar yet alien power pulsing within the massive aquamarine gem seemed to trail after him for a moment, before falling back with what felt like a mournful sigh. Bad Percy- don't personify bodily fluids, especially those of a crappy great-grandfather.

His path led him past the North gate of the inner dome, where light danced amidst the pearls embedded in the stone lattice-work, centered on the green jewels before extending out past the arrow loops on the first wall into the lake. By each one, there was a merman reclined on the accompanying sloped protrusions, armed and armored for a fight.

It took about a minute to reach the threshold of the external gate, and when he crossed it, Percy let himself sink until his feet rested on the bronze gate, savoring the pull of the whirlpool underneath. It tugged at him, ravenous and all-consuming, but deep within he could feel a miniscule shard of his dad's power, left behind when the god willed the eddy into existence with a passing thought.

When guards began grumbling quietly about the prolonging of the doors closing, Percy finally pushed off, flutter-kicking upwards. Beneath him, the retraction of the grate was silent, marked only by the dull thud of the gates slamming shut. About halfway up the outer dome, he paused to wave at one of the sentries through the narrow holes in the dome before continuing. Up close, the alternating vertical and horizontal blades that studded the fortress looked beautiful, reflecting the leyline's refracted light back and forth, like a forest of metal beneath a rainbow.

Percy reached the crest of the dome in short order, where he spied Triton free floating above ten feet above the skywards door. Wine-dark the depths lake may have been, but not even the deepest trench could obscure the sight of one of Poseidon's brood. The iridescent rays glittered off the heir's twin tails, tinting their normally green shade. Swallowing his hesitation like a multivitamin- really, would it have killed Hermes to make them gummies- Percy approached.

"Can we talk?"

Triton opened his black eyes and glared balefully. "I'd prefer not to."

"Yeah, same," Percy agreed, swimming closer but staying just out of trident-stabbing range.

"Yet here you are, still talking."

The half-blood hesitated. "I'm sorry. I shouldn't have mentioned her."

"No, you should not have. If you know what is good for you, you will never speak of her again."

Percy felt something vicious roil in his gut. You fucking started it. "Right back at you."

"It is not the same," Triton bit back. "I raised Pallas. I taught her to fish, to read the currents, to fight. She was my daughter, blood of my blood."

"Annabeth was my everything. We grew up together, traveled together, fought together. I followed her into the Pit and I would jump back in if it meant I could see her just one more time," snapped Percy, breathing heavily. He tasted bitter-sweet nightshade on his tongue.

The god sneered at him, trident manifesting in his right hand, pointing it at Percy. "You disgrace father's name with your affection for the owl spawn."

"She was better than her mother. So much better."

"Any loyal to one that is forsworn deserves nothing but death," Triton hissed.

Faster than the blink of an eye, Percy pulled out and uncapped his pen, freeing Riptide. "When she followed the Mark, she did so because the Greeks and Romans," the god's form flickered, olive skin darkening to the shade of seaweed before lightening again, "were at war, and the Earth Mother was waking. Her mother," he snarled venomously, "let Annabeth die to kill her own bane. Don't you dare compare her daughter to her." I came here to apologize but if you insult her one more time, I swear I will drown you.

Triton didn't attack, unfortunately; there was a well of Misery in Percy that ached to spring up and wrap around his divine half-brother in a wrathful, clawed embrace. Instead, the god just stared at him, onyx eyes strangely absent of the resentment that surfaced to meet Percy's reflection.

"My mind is unchanged," Triton said at last. Let's dance then, you- "But if you cannot control yourself at the mere mention of her, then I will be generous and refrain from doing so."

"Fine." Gee, thanks, let me give you a medal for deciding to not be a total asshole. All hail Triton, He-Who-Is-Less-Of-A-Jerk-Than-He-Could-Be. Still, probably the best I'm going to get from him.

The god squinted at him, as though he was actually expecting some kind of gratitude. "Fine?"

"Fine."

"Fine," growled Triton before turning away. "You're dismissed."

Percy took a moment to debate whether staying just to spite him was worth enduring his company. Yeah, no, absolutely not. "Don't stay out too late- pretty sure I saw Ursula floating around earlier." With that last parting shot, Percy willed the water to carry him away from the god and back down to the lakebed.

As he landed, feet sinking into silt, he saw, for the first time since the fortress's construction, the nereid of the lake, who was watching him in the distance. He waved, hesitantly, only for the sea nymph to dart away, her green light dimming as her tail propelled her closer to the surface. For a moment, Percy felt hollow, as though he'd lost something important, though he didn't know what it was.

He turned away and made his way back through the domes, past the dwindling crowds of merpeople, and into his cabin. All the children of Poseidon had one; the other mermen slept in barracks, albeit well-furnished ones. It reminded him of Camp Half-Blood, but not in a good way. After readying himself for bed, he slipped into his pod, closing the glass door and taking out Riptide. He pressed the tip of it against the pad of his thumb, sighing in relief as red drops rose, dissipating into a small, rust-colored fog. Capping his sword and sliding it back into his pocket, he counted Bessies until he drifted away.

In the lands of Morpheus, he found himself being hunted by a tall figure in a dark cloak, which billowed out behind it as it stalked Percy through a forest, which was dimly illuminated by what little moonlight filtered through. Only a pair of crimson eyes was visible beneath its hood, swirling round and round like a bloody undertow. The being didn't run, its strides long and languorous, but no matter how fast Percy fled, dodging trees and leaping over brooks and fallen logs, the figure was always half a step behind.

"Abandon hope," it hissed in his ear, putrid breath scented like decaying fruit and rotten corpses. "I am coming for you."