Location from The Library at Mount Char by Scott Hawkins
The realms beyond normal reality — dimensions, afterlives, and spaces between spaces that the librarians can access through the Library and that ordinary humans never know exist.
Beyond the Library and beyond the world that humans know, there are other spaces. The librarians call them the forgotten lands — not because they were forgotten, but because human minds are built to forget them. These are the realms where the dead go, where entities that aren't gods but aren't not-gods operate, where the rules of physics are suggestions rather than laws. Father could navigate these spaces freely. His children can access some of them through their catalogs — Margaret can walk into death's territory, David has fought his way through several layers of what might be called hell, and Carolyn suspects that the Library itself is a structure built in the forgotten lands and anchored to the physical world. Understanding these spaces is critical because Father's disappearance may have something to do with what lives in them.
The forgotten lands have no single appearance because they aren't a single place. They're a category — the spaces that exist outside the boundaries of human-accessible reality. Some look like landscapes from fever dreams: skies the wrong color, geometry that hurts to look at, horizons that curve up instead of down. Others are empty — vast voids with nothing in them except the sense that something very large is paying attention. Margaret and David navigate these spaces most comfortably — she because her catalog includes death's territories, he because his training sent him through them.
Also known as: the forgotten lands, the other places, beyond, the realms