the City That Forgot: Book 1 of Meridian Saga

A city built on forgetting. >Meridian survives by sealing its ghosts beneath glass, rail and rain. In the Undercity, courier Kael Voss runs routes that the official maps deny exist, one year after his sister Elian vanished in a rift surge everyone else has been ordered to forget. When a forbidden relic awakens the obsidian gauntlet fused to his arm, Kael hears six impossible worlds calling through the scar at the city's heart: sunfire citadels, drowned courts, living forests, machine cathedrals, neon masks and dreamlands made from guilt. Every faction wants to claim him. Every answer leads back to Elian. Inside a cathedral of white machinery waits The Hollow Saint, a faceless power that does not kill its victims - it erases them so completely that the world forgets it ever loved them. To save his sister, Kael must make Meridian remember what it buried, before the seventh door opens.