Many generations ago, the Wall was built to hold back the sea. A simple dam, it grew into a vast linear city, home to scholars, builders, and merchants.

But now days are growing shorter, temperatures colder, and in the wake of long winters come famine, destruction, and terror. As a mass exodus to warmer climes threatens to fracture Northland, one man believes he can outwit the cold and even salvage some scraps of the great civilization—before interminable gloom settles over the land; before the fires of war lay waste to an empire; before the ice comes....