“Lo, I see that which is beyond. I see the faces of pale moons and the fire of lost stars. I see the void un-walked and the waiting dark. I see the void that is my home and to which I return with hope and fear.”
—reputed words of unknown Rogue Trader departing Port Wander
The Koronus Expanse is the name given by the authorities of the Imperium of Man to a dangerous unexplored region of the Halo Stars located beyond the Calixis Sector in the Segmentum Obscurus. The Expanse is accessed through the Koronus Passage, a treacherous but navigable route through the great Warp Storms that bar passage to the Halo Stars beyond the way station of Port Wander on the edge of the Expanse. As is true of the Calixis Sector itself, the Expanse was untouched by the God-Emperor’s Great Crusade many millennia ago — and so it is a realm of fearsome xenos, treasures beyond imagining, heathen worlds of men, and the echoes of ancient doom.
The Koronus Expanse in the late 41st Millennium is a scattered, partly explored region on the frontier of the galaxy containing a few young Imperial colonies and vast natural wealth still barely exploited. Rogue Traders vie with one another for known resources, heedless of lives lost in the pursuit of riches, while a tentative attempt at Imperial colonisation follows in their wake. Drawn by the flow of wealth, pirates and servants of the Dark Gods have also slipped into the Expanse, eager to cast destruction upon the works of the God-Emperor’s faithful, living by what they wrest from dead hands, while the Expanse itself holds many secrets and native inhabitants no less dangerous.
For centuries, Rogue Traders have braved great evils and the treacherous warp to venture into the Koronus Expanse, but their efforts have barely begun to uncover its secrets. Footholds have been built close to the few semi-stable Warp routes into the area. Here, resource-rich worlds are exploited, xenos ruins excavated, trade envoys meet with heathen lords, and Imperial colonies are attempted upon sheltered worlds. This effort has been enough to shower wealth and fame upon the fortunate — and make corpses of the rest. The gateway to the Expanse is littered with broken vessels and tales of the vanished.
Beyond these human conflicts lie truly dark and dangerous voids, rife with rumoured terrors, undiscovered stars, and worlds of men who have never known the light of the God-Emperor. There are no defined Warp-routes, no safe ways through the swirling Empyrean. These regions hold the fearsome Ork, the treacherous Eldar, and strange ruins that lie beneath the light of dying stars.
The Warpspace of the Koronus Expanse is treacherous and unknown in the main, and the partially explored regions of the Expanse are islands of Imperial activity amidst a vastness of danger and mystery. Navigating is a far cry from traversing the well-established Warp routes of the Calixis Sector. Most of the Koronus Expanse is known to the Imperium only though legend, revelation, and hearsay. The Rogue Trader who ventures into this unknown risks his very soul upon the talent of his Navigator, and on the quality of what little information he has gleaned from those gone before.
Beyond the partly explored regions of the Koronus Expanse, past deeps beset by pirates and dread xenos, lie many worlds and strange phenomena which exist as the stuff of dark legend. Some of these uncharted stars were visited by a single Rogue Trader whose tales are doubted or dismissed by rivals as outright lies, while others are known only from dubious and apocryphal sources such as Thulean datavaults recovered from Dolorium’s voids in 741.M41, or the infamous prophetic visions of the Seven Witches of Footfall. Other fragments of contradictory lore relating to these dark zones are culled from even more untrustworthy sources, such as the muted astropathic whispers overheard on the Warp’s twisted eddies, the falsehoods of the deceitful Eldar, or the ancient myths of heathen worlds given over to darkness for millennia uncounted. Such areas are labelled only as “Here be monsters” on ancient charts, where only the foolhardy or insane would venture to seek their destiny.
Read a comprehensive history at: http://warhammer40k.wikia.com/wiki/Koronus_Expanse