Chalnath Expanse - History: The T'au Empire's Fourth Sphere Expansion unexpectedly emerged into realspace after the disastrous activation of their fleet's anti-matter-powered AL-38 Slipstream Modules created the Warp vortex known as the Startide Nexus, a stable, interdimensional pathway or "wormhole" between the region of the northern Segmentum Ultima the T'au named the Nem'yar Atoll and the primary territories of the T'au Empire to the galactic south in the Eastern Fringe near the Damocles Gulf.Once the T'au Empire confirmed the survival of the Fourth Sphere Expansion's fleet, Commander Shadowsun was given command of the Fifth Sphere Expansion and led it into the Startide Nexus. Once the Fifth Sphere Expansion fleet emerged into the Nem'yar Atoll, Shadowsun integrated the survivors of the Fourth Sphere Expansion fleet into her command and began expanding the size of the T'au Empire's new domain.Since its discovery by the T'au, the Nem'yar Atoll has become a cluster of Sept Worlds, stellar fortresses and orbital habitation spheres and cities that surround the Startide Nexus, but is also under almost-constant assault from raiders, hostile xenos and other, darker threats such as the forces of Chaos. As such, the military resources allocated to the defence of this key region by the T'au are now considerable, and ultimately led to conflict with the many Imperial worlds located in the same region, which the servants of the Emperor named the Chalnath Expanse.Commander Shadowsun soon attacked the Cardinal World of Astorgius while the Ctesiphus and Arrajian Systems were the site of major Genestealer Cult uprisings. On the Mining World of Haephos, the Imperial defenders engaged in a bitter guerrilla war against the Genestealer cultists and T'au infiltrators. The Riatov System became a cauldron of constant war between the T'au forces, the Astra Militarum regiments who called it home, and the Genestealer cultists.The Hive World of Vorotheion seemed immune to the violence for a time before becoming embroiled in a T'au invasion. The T'au wooed disenfranchised and discontented Human populations to the Greater Good, establishing insurrectionist cells and proxies to battle the Imperials alongside their conventional forces. The effects of the Psychic Awakening soon made themselves known on the Humans, with Ecclesiarchy priests performing "miracles" and even Gue'vesa being struck by bouts of emergent psyker-induced insanity.The disturbances on these worlds caused the Adepta Sororitas' Order Militant, the Order of the Sacred Rose, to respond, saving those who remained true to the Emperor while purging all Heretics and xenos they encountered. Warriors of the T'au Fire Caste put up formidable resistance, but the battle-sisters discovered that the greatest threat to the Emperor's rule in the region were the Ethereals accompanying the T'au forces, whose propaganda concerning the Greater Good was able to claim countless Human souls to their cause.Later, the Deathwatch of the nearby watch fortress of Mortguard under the command of Watch Master Agathon were drawn into the conflict after reports of rampant T'au and unexplained civil uprisings were made by the venerable Ordo Xenos Inquisitor Jazad D'ontor. Three full Watch Companies of Mortguard were ultimately deployed to the worlds of Arrajian IV, Cestis and Saint's Halt to aid the Imperial defenders in throwing back the T'au advance and cauterizing the Genestealer Cult infestations.Finally, drawn by the raging, three-sided conflict, massive Ork forces soon arrived in the region. They poured from the Ful'na Nebulae in ragtag invasion fleets. With the Thaxaril, Riatov, and Barolyr Systems barely pacified, the conflict continued to rage on half a dozen other fronts.Commander Shadowsun proved unwilling to allow this new menace to destabilise the precarious expansion of the Nem'yar Atoll into Imperial space. Deploying her forces in a complex web of interlocking positions throughout the Vy'las, Mets'ah, and Aso'da Systems, she began a Kauyon-style campaign on an interstellar scale. She planned to use this strategy to blunt the Greenskins' momentum and crush the threat they posed to the continuance of the Fifth Sphere Expansion.