Ad lit.org: Reading Discussion Guide: Midnight Over Sanctaphrax

Captain Twig learns that the Mother Storm is headed toward the Edge to re-seed the sacred waters of Riverrise, and thus rejuvenate all life forms throughout the land. This rare and natural occurrence would come as great news but for one dire problem: the floating city of Sanctaphrax stands in the path of the Mother Storm. Twig and his crew must return to the Edge and sever the anchor chain that ties Sanctaphrax to Undertown so that the buoyant rock on which the city is built can be released into Open Sky. It's up to Twig to accomplish this daunting task before the clock strikes midnight over Sanctaphrax.