The Void (usually but not always capitalized) is the 'empty' physical space in the D-Verse, which is to say, not occupied by celestial bodies or other significant quantities of matter.
Origin and purpose Edit
From the beginning of the D-Verse, the Void has always been the foundation or default state of physical existence. It vastly overshadows the volume of of physical space occupied by some sort of matter.
The purpose of the Void is simply to fill the delineated boundaries of the D-Verse with empty space for later use.
Physically, the Void is simply empty space, occasionally with insignificant quantities of matter. Aetherically, it is full of potential energy; the complete or near-complete lack of physical features results in an equally complete lack of restrictions on what physical features could possibly be created.
The potential energy also reverses the predicament faced by practitioners of elemental magic; while the four elements are nearly nonexistent in the Void, aether when used as a pseudo-element is not only powerful and widely available but also considerably less likely to cause scars or interfere with other aetheric patterns. It is for this reason that hybrid technology - including drive systems, Void weaponry, and other equipment and systems meant for use in the Void - functions on principles of aetheric elementalism, unless the engineers already have access to rune magic.