[Crystal Core Siege, Beneath the Gray Tide]

Gray mist engulfs Canglan City. Underwater reconnaissance packs hunt fishing boats, and Lu Chen takes his “originally adapted” younger brother, Lu Yang, on the run, trying to survive the pursuit by the Amethyst Society. Their father’s first-generation Amethyst notes reveal a hidden truth: Chen Yan’s backup vessel, a boy with the same birthmark as Lu Yang, is imprisoned on an isolated island, and the Mother Nest’s anchor point holds the key to releasing the gray mist across the globe. On the night of the full moon, when defenses are at their weakest, they must risk everything to destroy the anchor point. In this post-apocalyptic world, hope is forged with amethyst and their lives.