Then, rising up from the deep, there came a steady two-note beat. The beat of the chained bait beasts, who hauled the massive machines around. Like a thudding heart. Or beating wings. Louder the beat sounded, as if the wyverns down in the pits knew what was happening. It grew and grew, until it reached the cavern—until Asterin reached for her shield and joined in. Until each one of the Thirteen took up the beat. “You hear that? That is for you.”