The Manifold Sky, or simply Manifold is a multiverse with an unusual, non-euclidean geometry. The whole Manifold is a penteract - a five-dimensional cube - with all five spacial dimensions measuring roughly 50 miles in length. The Manifold is part of the Celestial System
which is, in turn, embedded in the Celestial Realms
The space within the Manifold Sky is actually a series of hollow three-dimensional cubes
, all of which are coterminous with other cubes to form tesseracts
(four-dimensional cubes these tesseracts are, in turn, coterminous with other tesseracts 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.