The space within the Manifold Sky is actually a series of hollow three-dimensional
cubes, all of which are situated coterminously with other cubes via the
commissures to form
tesseracts (four-dimensional cubes these tesseracts are, in turn, coterminous with other tesseracts via the
inflection layers to form a penteract (five-dimensional cube). The Manifold contains ten tesseracts subdivided into a total of 40 cubes, with each cube subdivided into two layers, each layer being "adjacent" to a different tesseract while still representing a part of the same cube.
Gravity has a much shorter effective range within Manifold Sky. Within each three-dimensional cube, the direction of gravity points towards the nearest face; in areas close to the junction of two or more faces (i.e. the vertices of the cube), the vector of gravity is the sum of those of the adjacent spaces (i.e. "down" points towards the corner near the vertices), meaning that mountain ridges tend to form along the edges and peaks near the vertices.
In the center of each face of a cube layer, a large fissure in the ground allows access to adjacent cube layers within the same tesseract. These terrain features are known as
commissures. Conversely, as a traveler approaches the geometric "center" of a given cube, directly between the layers of the cube, they approach an
inflection layer; once crossed, the traveler finds themselves descending into a cube layer within a different tesseract, with the cube layer they just left receding into the "center" of this new cube layer as they travel away from it.
This is a generalized map of the
Manifold Sky, with
cubes and
tesseracts shown based on their relative connections to one another. Tesseract labels are based on
Navigator's Guild nomenclature. Cube topology and geopolitical boundaries are excluded. Additional layers show various points of interest and the comfortable habitatats of the various sentient species within the Manifold. Note that the compass rose shows the progression of
day and night through the tesseracts, as well as the relative position of magnetic north (green arrow).
Successfully traversing the Manifold is tricky even with modern
dieseltech technology. The
Navigator's Guild has achieved near-universal presence in societies under the Manifold Sky by providing the knowledge required to safely travel between tesseracts and by suppressing the development of alternatives to their services. For this reason, many consider the Guild to secretly be the true rulers of the Manifold Sky, though the ruling classes of the many nations who regularly parley with them would never admit that out loud.