The dragon led them to a cleft in the mountains— a gaping wound in the rock, from which oozed a thick, black mist that coiled like living snakes. The air here was cold enough to sting, and the ground beneath their boots was sticky with a substance that reeked of iron and rot."This is it," the dragon's voice echoed in Lin Chen's mind, low and heavy. "The Well of Taint. The Sect dug it fifty years ago, using dark magic to tap into the dragon's old wounds. Every drop of taint here feeds on fear… and on the pact we broke."Lin Chen stepped closer to the cleft. Peering down, he saw a circular stone altar at the bottom— its surface covered in cracks, from which the black mist pulsed. Scattered around the altar were bones: human, animal, even fragments of what looked like dragon scales, all blackened and brittle."初代守护者 (The first guardian) tried to seal this," Uncle Wei said, pointing to carvings on the cleft walls. The images showed a man in golden armor pressing his palm to the altar, his blood dripping into its cracks— but the mist was already spilling out, wrapping around his legs. "He failed. The taint was too strong. So he used his own body to plug the well… for a time."Su Xiao knelt beside a bone fragment, brushing off the dirt. It was a small, curved scale— dragon scale, but not from the one beside them. "My grandmother wrote about this," she said, her voice quiet. "She came here once, with your father. They tried to purify the well, but the Sect attacked. Your father was injured… and my grandmother had to choose between saving him and sealing the well. She chose him."Lin Chen looked at the dragon. Its amber eyes were fixed on the altar, and its wings trembled. "She made the right choice," it said. "The first guardian's mistake was thinking he could fight alone. The pact is not about one person— it's about all of us."A sudden hiss cut through the air. The black mist at the bottom of the cleft swirled, merging into a towering figure: a humanoid shape made of taint, its body rippling like smoke, eyes glowing green. In its hands, it held a spear made of blackened bone— a fragment of the first guardian's armor, Lin Chen realized."Shadow Sect remnants," Uncle Wei snarled, drawing his bronze key. "They merged with the taint to become 'taint walkers'— worse than puppets. They don't die easily."The taint walker lunged, its spear stabbing toward Lin Chen. The dragon swiped its claw, slamming into the walker— but the misty body just reformed, laughing. "Foolish dragon," it gurgled. "You think you can stop what the Sect started? The taint is part of you now. It will always be part of you."Su Xiao pulled out her herb pouch— now refilled with moonwort she'd collected on the way— and crushed it into a powder. She threw it at the walker; the powder burst into silver flame, burning a hole in its chest. The walker screamed, but the mist quickly closed the gap."Purification isn't enough," Su Xiao yelled, her hands glowing with healer's light. "We need to seal the well— permanently. The carvings say we need guardian blood and healer's tears… but also something else. A piece of the pact."Lin Chen's bronze key hummed. He looked at the dragon, and suddenly understood. "A piece of you," he said. "The pact is between guardian and dragon. We need a piece of your magic to bind the seal."The dragon nodded. It lifted its paw, and a single scale detached from its leg— glowing gold, free of taint. It floated toward Lin Chen, who caught it in his palm. The scale was warm, like sunlight, and it pulsed in time with his key."Now," the dragon said. "Together."Lin Chen climbed down to the altar, Su Xiao and Uncle Wei covering him. The taint walker lunged again, but Uncle Wei's key shot a beam of golden light, pinning it to the wall. "Hurry!" he yelled. "The light won't hold it long!"Lin Chen pressed his palm to the altar— his blood seeped into the cracks. Su Xiao leaned down, a silver tear falling onto the blood; the two merged, glowing red. Lin Chen placed the dragon's scale on top, then drove his bronze key into the altar.A roar shook the mountain. Golden light burst from the altar, spreading up the cleft walls. The taint walker screamed as the light touched it, dissolving into black smoke that was sucked back into the well. The black mist coiled, then vanished, leaving the altar's cracks sealed with a layer of golden stone.The well was closed.Lin Chen climbed back up, his palm throbbing. The dragon nuzzled him, its amber eyes warm. "The pact is whole again," it said. "But the Sect is not done. They seek the '龙心碎片' (Dragon Heart Shard)— a piece of my heart that broke off when the Sect betrayed me. It's hidden in the old Suolong Village temple. If they find it, they can wake the taint again."Uncle Wei's face darkened. "Suolong Village. We thought we'd left that behind. But the Sect… they never stop."Su Xiao flipped through her grandmother's journal, stopping at a page with a sketch of the temple. "Grandmother drew this. The shard is hidden in the statue of the first guardian. She said it's protected by a spell— only someone with both guardian and healer blood can touch it."Lin Chen looked at his key, then at Su Xiao's dragon birthmark. "Us," he said. "We're the only ones who can get it first."The dragon spread its wings. "I will take you there," it said. "The Sect is already on their way. We don't have much time."They climbed onto the dragon's back— its scales were warm, and its wings beat softly, lifting them into the air. Below, the mountains stretched out, bathed in moonlight. Suolong Village was a dark smudge in the distance, but Lin Chen could already feel it— the taint's faint pull, the Sect's dark magic."We're really going back," Su Xiao said, her voice quiet. "After everything that happened there."Lin Chen nodded. "After everything that happened there. But this time, we're not running. We're finishing it."Uncle Wei clapped a hand on both their shoulders. "Your parents would be with us, if they could. But we're their legacy. And we're not going to let them down."The dragon flew toward Suolong Village, the moon at their backs. Lin Chen gripped his bronze key, the dragon's scale tucked into his pocket. He thought of the first guardian, of his father, of all the people who'd fought to protect the pact.The adventure wasn't over. The Sect was still out there, and the Dragon Heart Shard was waiting. But this time, they had each other. They had the dragon.They had the pact.Lin Chen looked down at the village, now growing closer. The temple's spire was visible, silhouetted against the moon."Let's go," he said.The dragon roared— not in rage, but in resolve— and dived toward Suolong Village.The final battle for the Dragon Heart Shard was about to begin.And this time, they were ready.