The Ksreskézaian—Hogedepi Expanse (variously: Ksreskézaian Expanse, Ksreskézaian–Hogedepi–Tletkettoyic Expanse, KH Expanse, KHT Expanse, KHX, KHTX, simply 'the Expanse', etc.), is a system of more than forty spacetime branes of extreme fragmentation that are densely interconnected, but largely isolated from the outside universe. Some branes contain only a single star; others several hundred. It is generally believed that the entire Expanse was once a single galactic arm many millions of years ago in a much larger brane, perhaps large enough to support galactic filaments and other cosmic structures, but today only a few fragments of that galaxy remain. Evidence for this is based on the common age and isotope distribution found in the stars of Globkhro, Rehal, and Batelta, the Expanse's three largest branes.

Although there are fragmented branes beyond the border of the Expanse, and arguably the effects of the fragmentation are much further-reaching than what are generally considered to be the Expanse's boundaries, the "Expanse" moniker is defined by ancient geopolitical boundaries that formed along the limits of the reach of the Thaumatic Manipulator Field, a remarkable technology that allows for the alteration of space, time, and matter. Both the Hogedepi and Tletkettoyi, their territories positioned at bottlenecks to the heart of the Expanse, grew to be highly dependent on this instrumentality, sequestering numerous other civilizations inside the field-affectable branes. It was not until the demise of the Tletkettoyi, at the end of the Grand War, that aeons of secrecy were ended, and it became possible to produce completely reliable astronavigational surveys of the Expanse's inner brane network.