The first rays of dawn painted the Big House a soft, hopeful gold, but inside, the air still hummed with the electric tension of the night's revelations. Percy, Nico, and Thalia sat around Chiron's table while having breakfast, their faces set with grim determination. The weight of the quest – Annabeth's soul, the world's balance – pressed heavily on them.

"So," Thalia began, running a hand through her spiky hair, "Kymopoleia's hiding in the 'uncharted, chaotic depths.' Getting there is our first problem. We don’t know her current whereabouts."

Nico, looking surprisingly fresh for someone who might have spent the night wrestling with the implications of his father's bargain, nodded. "I could try shadow traveling us. With Mrs. O'Leary, I might manage to get us close, even with the three of us."

Percy immediately shook his head. "No way, Nico. That'll vacuum most of your strength. You might get us there, but you'd be useless for the fight, or worse, pass out in the middle of god-knows-what kind of chaos."

Thalia chimed in. "Percy's right. The last thing we need is a comatose son of the underworld when we're trying to talk a primordial-essence-possessed sea goddess into sealing something away. We need you at full power." She looked at Percy. "A boat, then? You can navigate the weird currents, and I can provide better winds than you can."

Percy considered it. "A boat it is. But where do we even start looking for 'uncharted, chaotic depths'?"

Before they could delve into strategy, Corina stepped forward, her eyes bright with a desperate resolve. Cyrus, though silent, stood a step behind her, his posture conveying a readiness to assist. "We can guide you," Corina said, her voice surprisingly firm. "We know our mother's patterns, the places she favored even before...before the essence. We can lead you through the peripheral domains, at least to a safe distance from her direct hideouts. Once you locate her, Cyrus and I can return to camp."

Percy, Nico, and Thalia exchanged uneasy glances. The idea of bringing the volatile children of Kymopoleia on such a perilous journey, especially given their susceptibility, was deeply unsettling.

"Corina, Cyrus," Percy started, his voice firm, but a muscle twitched in his jaw as his gaze flickered to Cyrus. "Artemis was very clear. It's too dangerous. You're too vulnerable to her influence." His tone left unspoken the venom he still felt for Cyrus, the boy who had stolen everything from him.

"We understand the risk," Cyrus rumbled, his voice rough but devoid of its usual anger, meeting Percy’s gaze head-on. "But we know those waters in a way you can't. We feel them."

Thalia crossed her arms, her own discomfort evident. "And if you fall under her sway again? What then? We have enough problems without having to fight you two as well."

"Percy," Nico interjected, his voice low but insistent, stepping slightly closer to his friend. "He's right about their knowledge. This isn't just about fighting; it's about finding her in a place no one else can navigate. We need every advantage we can get. And frankly," he glanced at the twins, "it's probably safer for them to be with us, under our watchful eyes, than to be loose, potentially falling back under her influence without our knowing."

Thalia sighed, her resistance softening. "Look, Percy, I don't like it any more than you do, especially after...everything. But Nico's got a point. If they're the only ones who can guide us, then we're stuck. We take them, but we set very clear boundaries. One wrong move, and we tie them to the mast."

Before the persuasion could escalate further into that avenue, a younger camper from Cabin 11, looking a little overwhelmed, stumbled in. "Uh, sorry to interrupt. Package delivery. For Cyrus and Corina, from my dad." He held out a small, oddly heavy parcel wrapped in brown paper, bearing the winged shoe symbol of Hermes.

Cyrus took the package, unwrapping it with a furrowed brow. Inside were two sleek, silver life jackets, unlike any he’d ever seen. Attached was a simple, elegant note, written in Hermes's looping script:

Single use only. Must be worn at all times once in a boat. It will not work near 20.00008, -66.00001.

Cyrus's eyes widened, a flicker of recognition dawning. He glanced at Corina, then back at the note's coordinates. "The Puerto Rican Trench," he breathed, the words heavy with awe and dread. "This is where she is. We have to go, Percy. Corina and I are the only ones that can help to navigate there. Those waters won't listen to the Sea God, only to the influence of the Violent Storm and Waters Goddess and her offspring."

The finality in his voice, backed by the unexpected divine intervention, left no room for argument. The true nature of their destination, and the necessity of their unlikely guides, had just been sealed.

Percy ran a hand through his hair, the frustration and inner turmoil evident. His eyes, still holding that cold, distant light, rested on Cyrus. The animosity was still there, thick and suffocating, a constant reminder of Annabeth. But the pragmatism, the desperate need to find something to bring her back, began to outweigh his hatred. "Fine," he bit out, the word tasting like ash. "But you two step out of line, even once, and I swear, I'll throw you overboard myself. No gods, no monsters, no corrupted essences will save you."

Corina nodded, looking relieved. Cyrus simply held Percy's gaze, a flicker of something unreadable in his own eyes.

"Alright," Percy continued, pushing past the immediate tension. "We need a boat. A sturdy one. Something that can handle whatever uncharted or chaotic depths we might encounter." He looked towards Chiron. "Hephaestus cabin?"

Chiron stroked his beard, his brow furrowed. "Usually, yes. But since...Since Leo's death in the final encounter against Gaea, they haven't been at their best. Their spirit, their inventiveness, it's taken a heavy blow. They could build something, given time, but time is precisely what we don't have."

He paused, his gaze thoughtful as he looked at Percy. "Perhaps," Chiron suggested, his voice gaining a knowing quality, "a more direct approach is needed. One that connects to your own lineage, Percy. Given the nature of your quest and its ties to the sea's deepest, most chaotic currents...perhaps your father could provide what is necessary."

The revelation of their destination and the twins' undeniable necessity hung in the air, weighty and grim. Yet, as the sun climbed higher, casting the camp in its familiar, comforting glow, life at Half-Blood continued with a disquieting normalcy. Demigods bustled between cabins, chariots clattered in the arena, and the scent of ambrosia wafted from the dining pavilion. For the casual observer, it was just another day at camp, oblivious to the monstrous journey being planned within the Big House.

Inside Cabin Three, Percy sat on his bunk, his hand hovering over the conch shell on his bedside table. He'd tried sending an Iris-message to his father twice already, and both times the misty rainbow had dissolved into nothing but static. The sea, usually so responsive to him, felt distant, muted. He pressed his forehead against the cool shell, trying to focus, to pierce through the vastness, but all he felt was an echoing emptiness. Poseidon was either deliberately avoiding him or dealing with a crisis so immense it blocked even his son's desperate pleas.

Meanwhile, a few cabins over, the atmosphere was a mix of practical preparation and uneasy truce. Nico, with his usual efficiency, had started gathering supplies – Stygian iron daggers, pouches of drachmas, ambrosia, and nectar. Thalia, ever the pragmatist, was checking her bowstring, her electric blue eyes scanning the detailed map Chiron had provided, marking potential deep-sea currents. The twins, Corina and Cyrus, moved with a strange, quiet dignity. Corina meticulously organized small vials of what looked like purified sea water, perhaps for navigation, while Cyrus, surprisingly, sharpened his own trident with a whetstone, his movements precise and unreadable. They spoke little, but their presence was a constant, unsettling reminder of the treacherous alliance.

As dusk began to settle, painting the sky in hues of orange and purple, the campers gathered for dinner. The aroma of grilled hot dogs and s'mores filled the air, mingling with the earthy scent of the forest. Laughter and chatter rose around the crackling campfire, a temporary respite from the world's troubles. Percy sat slightly apart from his friends, picking at his food, his gaze lost in the dancing flames. He'd given up trying to contact his father for now. The silence from the sea god was deafening, leaving him feeling abandoned and even more alone.

A sudden, gentle thud near him, accompanied by the distinct scent of fish and fresh ocean, made Percy turn. He hadn't heard him approach, never did. Tyson, his younger half-brother, stood there, impossibly large and radiating a simple, comforting warmth. His single, huge brown eye, usually wide with innocence, held a hint of concern.

"Brother!" Tyson rumbled, his voice like rocks shifting underwater, a massive grin splitting his face. He wrapped Percy in a hug that threatened to crack his ribs, smelling of the deep ocean and freshly forged metal.

Percy gasped, then laughed, a real, unforced sound that surprised even himself. "Tyson! What are you doing here? I didn't even hear you!"

Tyson pulled back, his eye twinkling. "Daddy said– he sent me for a visit. Said you needed a break."