The Blight of Forgetting is spreading, its grey mist creeping deeper into the Whispering Woods. The Elderwood, a wise Custodian of Aevum, reveals that ancient knowledge held within the legendary Sunken City of Lyra might be their only hope. Once a magnificent metropolis built by powerful magic-users, Lyra now lies submerged beneath a mystical, glowing sea within Aevum, its spires and domes occasionally breaching the surface.Leo, Maya, and Finn embark on a perilous journey across Aevum's unpredictable waters, navigating the elusive Shifting Isles and encountering strange, new creatures. As they descend into the silent depths of Lyra, they discover not only breathtaking architecture and lost artifacts, but also the lingering, fragmented Echo of one of the original Architects. This echo holds crucial knowledge about Aevum's essence and the true nature of the Blight.But the Echo Collectors are also drawn to Lyra's powerful, ancient memories, their presence more chilling and active than ever. The Sunken City's Secret is a thrilling underwater adventure where the children must outwit the Collectors, decipher ancient puzzles, and uncover the truth that could save Aevum, before Lyra's secrets are lost forever.