Chen Jiuzhang planted his feet firmly on the trembling platform, the crystal - key held high above his head. Its light wavered as if struggling against an invisible force, but he steeled his resolve. The dark tendrils in the sky writhed like living things, each one pulsating with a malevolent energy that seemed to eat away at the very fabric of the realm."Su Nian, Zhang Chengying, keep that thing distracted!" he shouted, his voice barely audible over the roaring wind whipped up by the entity's growing power. "Lyra, if I falter, use whatever magic you have left to boost the key's energy!"Su Nian gave a sharp nod, her chains already spinning. "Leave it to us!" she hollered, and with a powerful leap, she launched herself towards the colossal entity once more. The chains wrapped around its neck, and she yanked with all her might, trying to turn its attention away from Chen Jiuzhang. Zhang Chengying followed suit, slamming his hands onto the ground. Runes flared to life, and a wall of earth shot up, crashing into the entity's legs.The entity let out a furious howl, swatting at Su Nian and sending her flying. But she quickly recovered, using her chains to swing back into the fray. Meanwhile, Zhang Chengying was locked in a struggle to keep the earth magic stable as the entity stomped on the ground, attempting to shatter the runic barrier.Lyra positioned herself beside Chen Jiuzhang, her hands hovering over the crystal - key. Her body trembled with exhaustion, but her gaze was fixed on the sky. "I'm ready," she said through gritted teeth.Chen Jiuzhang closed his eyes, delving deep into the connection he felt with the key. Images of ancient guardians and forgotten rituals flashed through his mind. He began to chant in a language he'd never spoken before, and the key responded, its light flaring bright enough to blind. A beam of pure energy shot towards the cracks in the sky, but the dark tendrils lashed out, wrapping around the beam and trying to snuff it out.The entity, sensing the threat to its newfound power source, redoubled its efforts. It released a deafening sonic boom that shattered the earth - magic wall and sent Zhang Chengying crashing into a nearby rock formation. Su Nian was caught in the blast, her chains flying loose as she was thrown across the platform.Lyra's hands glowed with silver energy as she poured everything she had into enhancing the key's power. The combined force pushed back against the dark tendrils, but they were resilient, and more of them emerged from the cracks, their numbers multiplying.Blood trickled from Chen Jiuzhang's nose and ears as the strain of channeling the key's energy took its toll. His vision blurred, but he refused to give up. "Just... a little more," he gasped, his voice a ragged whisper. The group was on the brink of collapse, and the fate of the Gui Xu Secret Realm hung by a thread as the battle between the light of the crystal - key and the encroaching darkness reached its most intense moment.