Segmentum Obscurus

The Segmentum Obscurus, also known as the Segmentum Obscura, is the region of Imperial space to the galactic north of Terra. This Segmentum of the Imperium of Man is the home of the vast Warp Storm and Warp Rift called the Eye of Terror, the primary home for the Forces of Chaos in the Milky Way Galaxy. The Imperial Navy's Segmentum fleet headquarters is located in the Cypra Mundi System, which also serves as the central headquarters of the Imperial military's Segmentum Command. The Segmentum Obscurus is the area of the Imperium most often under deadly threat by attacks from the Eye of Terror and is also the site for all of Abaddon the Despoiler's Black Crusades. As such, it currently is home to the majority of the Imperium's armed forces, which were most recently mobilised to a state of readiness not seen since the Horus Heresy as a result of the 13th Black Crusade in 999.M41.

Sectors

 * Agripinaa Sector
 * Cadian Sector - The Cadian Sector is the most heavily fortified sector in Imperial space, as it is the home of the Cadian Gate, the only clear route out of the Eye of Terror and into Imperial territory. The Fortress World of Cadia stands at the center of the sector and its people serve as the unflinching sentinels of the Cadian Gate. Portions of Cadia are currently occupied by the Forces of Chaos, following the indecisive outcome of the 13th Black Crusade in 999.M41. Cadia is currently circled by several Imperial Navy battlefleets and the maintenance of this space superiority is all that is keeping the Forces of Chaos from staging their first breakout into Imperial space in force since the end of the Horus Heresy.
 * Calixis Sector - The Calixis Sector is a sector of the Milky Way Galaxy that serves as the setting for the Warhammer 40,000: Dark Heresy role-playing game, which focuses on the actions of Imperial Inquisitors and their chosen Acolytes and Throne Agents. The Calixis Sector is an Imperial sector located in the Segmentum Obscurus on the northern edge of the known galaxy, near the Halo Stars and the Eye of Terror. To the trailing edge of the galaxy, the Calixis Sector is bordered by the hazardous territories of the Fydae Great Cloud and to spinward by the Scarus Sector. Bordering to coreward, its immediate neighbour is the Ixaniad Sector. To rimward lie the contested and unregulated Imperial frontiers of the Halo Stars where humans and xenos mix in the quest for power and profit in the infamous Koronus Expanse. Conquered by Lord Militant Angevin for the Imperium of Man almost two thousand years ago in the 39th Millennium during what became known as the Angevin Crusade, the Calixis Sector contains many heavily populated and important worlds, though it lies a great distance from the Imperium's core sectors. The sector's first Imperial Sector Governor was Drusus, one of Angevin’s most capable generals, a man now revered as a Saint of the Imperial Cult.
 * Gothic Sector- The Gothic Sector of the ]]Milky Way Galaxy is a sector of the Imperium of Man in the Segmentum Obscurus to the galactic North of Terra that is located on the border with the vast Ultima Segmentum. The Gothic Sector lies adjacent to the great Warp rift known as the Eye of Terror and was the location where Abaddon the Despoiler's 12th Black Crusade, colloquially remembered as the Gothic War, was fought from 139.M41 until 160.M41. The Forces of Chaos were defeated by the Imperium during that conflict, but Abaddon managed to seize several of the Blackstone Fortresses which he would use to eke out a more successful conclusion over 800 standard years later when he launched the 13th Black Crusade in 999.M41. The Gothic Sector and the Gothic War was also the setting for Games Workshop's tabletop game of starship combat, Battlefleet Gothic.
 * Ixaniad Sector
 * Scarus Sector - The Scarus Sector is a division of the Segmentum Obscurus close to the Eye of Terror. Its sector capital is the hive world of Eustis Majorus. The Scarus Sector borders the Calixis Sector to spinward and its known sub-sectors include Helican, Antimar, Angelus and Ophidian. This sector is the theatre of operation for the renowned Inquisitors Gregor Eisenhorn and Ravenor. The Helican sub-sector is the site of the Helican Scism, a wave of rebellion, terrorism and sabotage that swept the area. The Ophidian Subsector is noted for being the site of the Ophidian Campaign (also known as the Purge Campaign), in which Battlefleet Scarus wrested control of the sub-sector from heretic forces. The campaign lasted from 240.M41 to 337/338.M41 — a considerable achievement in such a short timescale. Lately, the Scarus Sector has been plagued by invasions of Orks, who attacked en masse during the 13th Black Crusade (a campaign led from the Eye of Terror by Abaddon the Despoiler himself) and Greenskin infestation remains a very real problem in this corner of the Imperium of Man.

Notable Systems

 * Gildar System

Notable Worlds

 * Cadia (Hive World/Homeworld Cadian Imperial Guard Regiments) -
 * Caliban (Death World (Destroyed)/Former Chapter Homeworld Dark Angels
 * Fenris (Death World/Astartes Fortress Monastery Space Wolves)
 * Medusa (Feral World/Astartes Fortress Monastery Iron Hands)
 * Mordian] (Hive World/Homeworld Mordian Iron Guard Imperial Guard Regiments)
 * Scintilla (Hive World/Sector Capital Calixis Sector)
 * Vostroya (Industrial World/Homeworld Vostroyan Firstborn Imperial Guard Regiments)

Notable Celestial Bodies

 * Blackshine Nebula
 * Eye of Terror
 * Halo Stars