The Machinery knows all. For ten millennia, the leaders of the Overland have been Selected by the Machinery, an omnipotent machine gifted to the world in darker days. The Overland has thrived, crushing all enemies. But the Machinery came with a prophecy: it will break in its ten-thousandth year, Selecting just one leader who will bring Ruin to the world. That time has arrived. Katrina Paprissi is an Apprentice Watcher, charged with seeking out any who doubt the power of the Machinery. But as the Machinery nears breaking point, her own doubts begin to surface. She must travel to its home in the depths of the mysterious Underland, to see if Ruin really is coming for them all...