The Sol System is the birthplace of humanity and the sacred heart of the Imperium, the star system that cradles Holy Terra, the Throneworld from which the Emperor's will radiates across the galaxy. No place in the material universe is more revered, for here the human species first arose and here its immortal master endures upon the Golden Throne.
The system is a fortress without equal. Its worlds and void-stations bristle with defenses, and its every approach is watched by fleets, orbital batteries, and the vigilant guardians of the Throneworld. Beyond Terra lies Mars, the sacred forge world of the Adeptus Mechanicus, and between these two ancient powers the Sol System forms the twin pillars upon which the entire Imperium rests.
Humanity's first steps beyond its cradle were taken here, from the settlement of Luna to the taming of distant moons, and the system remains dense with the relics and installations of ten thousand years of history. To dwell within Sol is to live at the very center of the human universe, in the shadow of the Emperor himself. It is the most heavily defended and jealously guarded region in the galaxy, for should Sol ever fall, the Imperium and the species that built it would fall with it.