The transition from the rock shaft into the unmapped network of the drainage flues did not offer the relief of open space; it merely swapped the choking salt dust for a damp, low-pressure chill that smelled of old river silt, stagnant grease, and decaying timber framework. The walls here were rough-hewn stone blocks, green with slick river moss, weeping continuous streams of cold water that gathered in deep, stagnant pools between the rotting floorboards.
The low, mechanical hum of the automated sweeping engine behind them faded into a muffled, thrumming vibration that rattled the iron pipes overhead, but the air remained static, heavy, and thin.
