The Windsmith Elegy is set on Earth between 1899-1939 and Shadow World, a Secondary World consisting of four main domains, named after the Cardinal Winds: Hyper-Eurus; Hyper-Zephyrus; Hyper-Notus; and Hyper-Borea.
The prophet Mani, founder of Manichaeism, imagined that the world was once divided between a kingdom of darkness and a kingdom of light, existing separately but adjacently, and that, as the result of darkness's inherent aggression, these two kingdoms had become confused and jumbled, creating the world we know now, which he called "the Smudge". He thought it was the duty of all people on the side of light to recover those atoms of their substance from the darkness and thus, in however small a way, do their bit to rescue the world. If one lived a "good" life, one was helping to do no less than protect the vastness of the world and everything in it, past, present and future; one would become, in effect, absorbed into God.