Planar Void

The basic tenets of Planar Theory hold that beyond our Plane of Abiding there is a multitude of other planes, each operating off of different physical laws of existence and reality than what laws govern our world. These various planes, while interconnected with the most inordinately complex of patterns, do not touch directly -- there is a layer of Planar Void (defined as the absence of all existence) which separates each, serving as a wall and boundary.

There is, however, some transfusion between the planes. They resonate with each other, and objects and energy (ie mana) are capable of passing between them through certain points. It is necessary that the boundaries between each remain stable and firm. Our world would cease to exist as we know it -- if, in fact, it continued to exist at all -- should it come into full and complete contact with another plane, in the sense of the wall between the two being torn apart and the two colliding and coexisting without the separation of the absence of all existence, which is the Planar Void.

Attempts at harming these boundaries pose great risks of damage to reality itself, and renders our plane susceptible to the attacks of extraplanar beings. Perhaps the most well-known example of such an attack is the presence of the "Nameless Evil of Zaulfung", later revealed to be the demon Maelshyve, who gained foothold within the Plane of Abiding after a rupture in the Planar Void surrounding our plane.