Dark Marches - The Dark Marches lie at the very borders of the Segmentum and are spread in an arcing band across the borders of the Veiled Region. Consisting of some of the oldest planetary systems within the entire galaxy, the Dark Marches were amongst the last regions of the Segmentum to be attached to the Imperium of Mankind as they were only conquered and colonized after the Age of Apostasy during the Dark Marches Crusade.
Garon Nebula - This nebula is located in the southern region of the Segmentum Tempestus within the largely unexplored tract of wilderness space called the Veiled Region by Imperial astrocartographers. This nebula encompasses the Hell Stars, and was the site of the ill-fated Garon Nebula Crusade of the Black TemplarsSpace MarineChapter.
Hell Stars - This group of star systems resides in the Garon Nebula.
Ophidium Gulf - This region lies to the galactic south of the Segmentum Tempestus.
Amerikon Sector - The Imperial BattleshipMerciless Death disappeared in this sector.
Caligari Sector - The Caligari Sector is a vast, ancient and forgotten region in the Segmentum Tempestus, filled with shadows that hide hundreds of tainted worlds. It is a sector plagued by the mysterious Warpsurges, which are smaller, but highly unpredictable manifestations of the dreaded Warp Storms. Far from the guiding light of the Astronomican and torn apart by the foul tempests that can twist reality and cut off entire star systems for centuries, leaving them ripe for Chaos infestation, the Caligari Sector is a haven for the Heretic, the outlaw and the corrupted.
Coptis Sector - The planet Karis Cephalon, an Imperial world and the site of an astrological convergence lies in the Coptis Sector. The mutant slave labor trade in this sector was broken up by the InquisitorTyrus. "The Angel," an ancient weapon from the Dark Age of Technology, was hidden within the catacombs under the Amethyst Palace, the heart of Karis Cephalon's capital city, which is centered around the pre-Imperial construct known as the Needle of Sennamis (a possible psychic amplifier). The sector was resettled by the Imperium during the Great Crusade in the early 31st Millennium. The sector lies 5,300 light years from Terra.
Donorian Sector - This sector is home to several alien races, including the K'Nib and the Clawed Fiend. The Donorian Sector may also lie partly in the Segmentum Solar.
Eurydice Sector - Founded following the Age of Apostasy in the 36th Millennium, the Eurydice Sector was born only after the famed Dark Marches Crusade had liberated its worlds from the multitude of xenos lifeforms that had dominated it for so long. Following the untimely demise of the Orpheus Sector, the Eurydice Sector has been constantly reinforced in order to form a bulwark against the emerging threat of the Necrons.
Forsarr Sector - A long established Sector Imperialis which contains the homeworld of the First Foundation Chapter of the Raven Guard, Deliverance. Due to its proximity to the Ork-Empire of Octavius, the Forsarr-Sector has increasingly suffered from the Orks' violent migrations known as WAAAGHs.
Haxan Sector - One of the four new sectors founded in M36 following the Dark Marches Crusade.
Leyak Sector - One of the four new sectors founded in M36 following the Dark Marches Crusade. As of 976.M37 all contact with the Leyak Sector has been lost.
Orpheus Sector - The Orpheus Sector was a Sector Imperialis of the Segmentum Tempestus. This fortress realm had endured for nearly four thousand years against the ravages of the Ork and the predations of the Eldar. The destruction of civil war and the malevolence of Chaos, would yet prove to be as defenceless as a new-born before the horror of what was to come -- the NecronMaynarkh Dynasty. Awakened from their slumber, this malevolent and sinister Necrontyr dynasty was known for its savagery and malice. Emerging from their millennia-long stasis sleep, the Maynarkh pursued their unnatural lust for destruction and bloodshed. After years of probing and study, eventually this Necron dynasty first made contact with the Imperium in the Orpheus Sector, which resulted in the ongoing Orphean War. Despite the mobilisation of the sector's Imperial Navy Battlefleet Orpheus, multiple Imperial Guard regiments and local Planetary Defence Forces, it was still not enough to halt the xenos onslaught. Even with the help of multiple Space Marine Chapters, including the Minotaurs, Marauders, Nemesis Chapter, Red Seraphs and the Angels Revenant, was not enough to stem the Necron tide. By 995.M41, three years after the conflict began, the war had become unsustainable, with attrition losses reaching 60%. Segmentum Command believes the Orpheus Sector cannot be saved without a Crusade-level campaign, which would take the Imperium a minimum of thirty years to organise. Faced with such dire prospects, Imperial war savants and strategists believe the only viable option left is to enact Exterminatus.
Spartus Sector - The planet Jericho III had its capital city destroyed by a Dark Eldar raid that resulted in the deaths of over 20,000 inhabitants and the hideous enslavement of countless others. The Dark Eldar next raided the Forge World of Stratix's polar arsenal, and stole experimental Imperial military hardware. The planet Vistro in the sector was the destination of an Imperial convoy that was also attacked by the Dark Eldar, who stole strategic ores from the Imperial freighters before destroying several of them outright.
Uhulis Sector - The Uhulis Sector is an important Sector within the Segmentum Tempestus and mostly consist of overpopulated Hive Worlds and other stategically important worlds. Due to its proximity to the now lost Orpheus Sector, the Uhulis Sector contributed vastly in the colonization progress that began in the Haxan, Leyak, Eurydice and Orpheus Sectors in the wake of the Dark Marches Crusade. In the mid 32nd Millennium, the Sector was ravaged by the Ork populated Space Hulk known as "Da Iron Worm", leading to the loss of the Fortress World of Armstrong and Velgagrad, and perhaps more importantly the Forge World of Temaxia.
Barnardi Prime System - This star system, and those surrounding it, were home to the Narnardi Conflict, which involved the infamous ChaosBattleshipMerciless Death.
Gerat System - Located in the Agritha Subsector, the Gerat System is a solar system of seven planets, all resolving around a single type L-V orange dwarf star. The system main world is Geratomro, which tried to seceed from the Imperium in 389.M41 before being brought back into the fold by the combined forces of the Astra Militarium and the Black Templars.
Forsarr - The Hive World of Forsarr is the capital of the Forsarr-Sector, recently invaded by the Orks of WAAAGH! Garaghak.
Geratomro - In 389.M41, this once-loyal Industrial World was the theatre of the Geratomran Reconquest, a brief but savage military campaign which saw the forces of the Imperium narrowly avoid a full-fledged daemonic incursion.
Kurzon's Fall- Kurzon's Fall is an Imperial Jungle World. Dark Eldar attacks upon its settlements prompted the Cardinal of the neighboring Cardinal World of Sanctus Prima to call for a War of Faith against all aliens in the Orpheus Sector.
Phobian - Chapter homeworld of the Dark Hunters Space Marine Chapter
Raas Bisor - This is an Imperial Guard Foundry World.
Rynn's World - Rynn's World is an Imperial Agri-World that is also the homeworld of the Crimson FistsSpace MarinesChapter. It and the Rynnstar System of which it is a part were both named for the Imperial Reclamator Saldano Malverro Rynn who first led Imperial colonists to the system, reclaimed Rynnsworld for Mankind and settled it as another Imperial Agri-World. The planet is sparsely populated, mountainous, and devoted to intensive agriculture. Due to its distance from other Imperial worlds and its proximity to Ork-controlled space, it is somewhat isolated from the rest of Imperium, with the closest neighbouring human planet being Badlanding. The Crimson Fists' Fortress-MonasteryArx Tyrannus has stood on Rynn's World for over a thousand years since their great Battle-BargeRutilus Tyrannus was dismantled to build it after the Crimson Fists were granted Rynn's World as their fief and ceased being a Fleet-based Chapter in 740.M40. Though serving as the Chapter's homeworld, Rynn's World is not owned as a Chapter fief by the Crimson Fists, and has its own Planetary Governor. Before a devastating invasion by Orks, the planet was protected by a formidable missile defence system, designed to deter invaders and a relatively skilled Planetary Defence Force called the Rynnsguard. Unfortunately, Rynn's World is not so far from the OrkEmpire of Charadon. As the Ork empire grew, Rynn's World began to present a tempting target to Charadon's ruler, Snagrod the Arch-Arsonist. The planet was finally invaded in 989.M41 by Charadonian Orks under the orders of Snagrod. In a freak accident, the Crimson Fists' fortress-monastery was destroyed in the initial invasion by one of the Chapter's own defence missiles that went rogue and the Chapter was all but wiped out. Without the protection of the Crimson Fists, the humans of Rynn's World were quickly slain, and their settlements, with the exception of New Rynn City, the planet's capital, were completely overrun. Rynn's World was eventually liberated by the Imperium, although it took years of fighting to reconquer the worlds in Loki Sector under Ork domination.
Targis VIII - This Hive World is locked in perpetual night and lies on the fringes of the Halo Stars in the galactic south. A large WAAAGH! of several Ork Warlords were defeated here by the Astartes of the Raven Guard. Notable Shadow Captain Kayvaan Shrike first rose to prominence for his actions during this Imperial campaign.
Solstice - This world is notable for the victory of the inspirational Imperial missionary Uriah Jacobus over a cult of Genestealers. Jacobus was notable for converting a number of worlds in a remote area of the galaxy. He earned a reputation for facing the worst odds and still emerging victorious.
Tallarn - This Desert World which circles two orange suns was fertile until it was virus-bombed by the Iron Warriors during the Horus Heresy, but is now covered with sulpherous sand, with its inhabitants living in domed cities or underground caverns. At the Ka'an Salient during the Iron Warriors' invasion, 50,000 tanks clashed in largest tank battle on record in Imperial history. Tall vapor-trap towers rise over the settlements. Human discovery of the Warp Gate known as the Cursus of Alganar brought on an Eldar attack before the Warp Gate could be opened to a Chaos horde. The humans of Tallarn and the Eldar united against the common foe and resealed the Cursus, locking away its daemonic protectors. The Imperial Guard's Desert Raiders regiments fought the forces of Slaanesh at the site of the Cursus as did the Titans of the Legio Mortis.
Tethrock Quay - Imperial Naval Outpost. There are reliable reports of increasing Necron activity in this region of the Segmentum.
Volistad - Volistad is a human-settled world that was first colonised by the Imperium in 979.M35. However, the history of Volistad at this point is unknown. Warp Storms isolated the planet while still in its sociological infancy, and it was left to develop on its own for the next 3,500 Terran years. Volistad was only re-discovered by the Imperium in 437.M39.