Onyx felt the water go cold before she saw the shape. She was the oldest of the sisters, the one who spoke to sea creatures, and tonight she needed that gift more than ever. She had come to the deep to prove herself to the moon goddess. She wanted legs. She wanted to walk the shore at will. But the goddess did not answer weak hearts, and something huge was rising beneath her. The sea serpent uncoiled from the dark. Its body was black and sleek, longer than her father's throne hall. One orange eye fixed on her. It opened a mouth full of teeth and lashed the current, dragging her deeper by the pull of its wake. Onyx fought upward, but the water spun her like a leaf. "Onyx!" Lunara reached her first. Her white hair streamed as she caught Onyx's wrist. Lunara's silver tail flashed hard against the current. "You can't fight it. It's stronger than all of us." Marina swam close behind, green hair tangling around the shells at her neck. "Then talk to it," Marina said. "You're the only one who can." Onyx's chest burned. She looked into the serpent's eye and reached for the old gift, the one that let her hear beasts the way she heard her sisters. She pressed her voice into the water. "Be still. I am not your enemy." The serpent hissed and struck. Its tail slammed her ribs. Pain white-flashed through her, and the truth landed with it: this creature was not angry. It was afraid. Something had driven it up from the trenches, into waters it did not know. Onyx stopped fighting. She let the current turn her toward the serpent. "You're lost," she said softly. "Something below scared you. I feel it too." The orange eye blinked. The lashing slowed. Then came a low moan through the water, one Onyx knew by heart. Her own creature swept up from the deep, the long dark sea-beast she had tamed as a hatchling and raised at her side. It curved its serpentine neck between Onyx and the intruder. It did not attack. It simply held, calm and huge, a wall of quiet in the churning water. The sea serpent studied the gentle giant. Slowly its coils loosened. Onyx swam forward and laid her palm flat on its cold snout. "Go home," she said. "The shallows aren't safe for you." The serpent shuddered, turned, and dove. The dark swallowed it. Onyx floated, ribs aching, breathing hard. Lunara and Marina reached her, pale with relief. "You did it," Marina whispered. But Onyx stared at the black trench where the serpent had fled. It had not come to torment her kingdom. It had run from something worse below. Her hand tightened on her old friend's neck. Whatever had frightened a monster like that was still down there, waiting. And the moon goddess would judge her by how she faced it.