Segmentum Obscurus - Notable Worlds: Agripinaa (Forge World) - Agripinaa, known as the "Orb of a Million Scars," is a notable Adeptus Mechanicus Forge World located in the Agripinaa Sector. This world primarily provided materials for the Cadian front and its industrial heartland is solely engaged in the production of ammunition. Located near the Eye of Terror and assaulted by the Chaos forces of Abaddon the Despoiler during the 13th Black Crusade, Agripinaa did not weather the attacks of the Forces of Chaos well and much of its industrial heartland was laid to waste.Belial IV (Crone World) - The world of Belial IV was one of the early Aeldari Maiden Worlds, but when it was pulled towards the Eye of Terror during the Fall of the Aeldari, it became a deserted and abandoned Crone World. It is said to be home to a sacred Aeldari artefact of black crystal, one of the Crone Swords forged from the energies of death now desperately sought by the Ynnari.Belis Corona (Dead World / Segmentum Battlefleet Headquarters) - Belis Corona is an Imperial Dead World located near the Eye of Terror, which serves as the Segmentum Obscurus' primary base for the Imperial Navy's Battlefleet Obscurus as well as the Imperium's administrative capital for the entire Segmentum. There is a vast conglomeration of orbital dockyards in geosynchronous orbit about Belis Corona where entire sector battlefleets can be serviced and refitted. Massive stockpiles of munitions, supplies and other war materiel are stored in armoured bunkers buried many kilometres below the planet's barren surface.Cadia (Fortress World) - Cadia, officially known as Cadia Prime, was a terrestrial, Earth-like planet that has been classified as both a Civilised World and as the Imperium of Man's most important Fortress World by the Administratum. It guards the only known navigable route to and from the massive Warp rift known as the Eye of Terror, a passage called the Cadian Gate. The world's dangerous proximity to the Eye of Terror made it necessary for the people of Cadia to heavily fortify the planet. Cadia was always the first target of the Chaos Warmaster Abaddon the Despoiler's assaults and Black Crusades, when the Forces of Chaos Undivided launched themselves from the Eye of Terror every few centuries in an attempt to break out and invade the Imperium proper as they did during the Horus Heresy. Cadia's natural environment was much like Terra's was millennia ago, with a large ocean covering 70 percent of the planet's surface. The land mass that did exist was divided between incredibly thick pine forests and vast glaciers. The planet was slightly cooler than most human-settled worlds but not to the point that it adversely affected growing conditions. Settled before the onset of the Age of Strife by a branch of humanity that eventually fell to the worship of the Chaos Gods and played a major role in the ultimate corruption of the Space Marine Legions, Cadia was re-settled sometime in the early 32nd Millennium by Loyalist humans of the Imperium. The world's landscape was dotted by strange black pylons of clear xenos origin called the Cadian Pylons. These devices were actually constructed by the Necrons millions of Terran years ago to hold back the psychic energies of the Eye of Terror from the world, which was an ancient Necron military base during their war with the Old Ones. The Cadian Pylons and other similar devices on worlds in the region were what created the unusual area of realspace stability known as the Cadian Gate near the Eye of Terror that is unaffected by the constant Warp Storms that surround that Warp rift. Cadia's location directly adjacent to the dangerous Eye of Terror has made it necessary for the people of Cadia to fortify the planet to an extent where almost the entire population lives in massive fortress-cities known locally as "Kasr". Thus Cadia has an odd mix of dense urban areas and vast open tundras and other natural landscapes. During the 13th Black Crusade in 999.M41, Cadia finally fell to the assault of Abaddon the Despoiler. Only a few million managed to flee off-world before it was consumed by the energies of the expanding Eye of Terror. Many of these refugees made their way to the Agripinaa System's world of Chaeros, which was renamed New Cadia.Caliban (Death World/Former Chapter Homeworld of the Dark Angels) - Caliban was an Imperial Death World located in the Segmentum Obscurus to the galactic north of the Eye of Terror that was once the homeworld of the Dark Angels Legion of Space Marines, which was destroyed during the conflict between Luther, his Chaos-corrupted Fallen Angels and their Primarch Lion El'Jonson and his Loyalist Dark Angels in a great conflagration immediately following the end of the Horus Heresy. What little remained of the planet was the territory surrounding the fortress-monastery of the Dark Angels, which was transformed into a mobile star fortress that serves as the primary fortress-monastery and base of operations of the Chapter at present and is known informally as The Rock.Chinchare (Mining World) - An asteroid locked in a figure of eight orbit around a binary star. It was once home to a creature of Chaos formed from the coagulated bodies of pilgrims who had descended into the asteroid to worship a corrupted crystal structure known as the Lith. The creature was later destroyed by Inquisitor Gregor Eisenhorn and Magos Geard Bure. This asteroid possesses a wealth of ultra-rare metals such as ancylitum and phorydnum, and supported a workforce of almost 3,000 miners and associated staff. During the 13th Black Crusade, contact with this isolated world was lost. Its current status is unknown.Fenris (Death World) - Fenris is the Death World in the Segmentum Obscurus that is the homeworld and recruiting ground for the Space Wolves Space Marines Chapter and of their Primarch Leman Russ. Fenris takes its name from the mythical Norse wolf fathered by the god of tricksters Loki that would assault the Norse gods during the Final Battle of Raganarok. Most of the names of locations on Fenris are also drawn from the Norse mythology and languages of Old Earth. Fenris is situated in the galactic south of the Segmentum Obscurus, at the end of the Warp rift known as the Eye of Terror, from which come the Forces of Chaos to raid and pillage. Fenris thus lies at the forefront of the Imperium's defence against Chaos. The Space Wolves maintain the vigil that began many millennia ago at the close of the Horus Heresy and watch over a hundred other worlds besides. Their domain stretches far and wide across the scattered stars that girdle the Fenrisian star system, but it is the bitterly cold Death World at its heart that the Space Wolves proudly call home.Hydra Cordatus (Forge World / Desert World) - An Imperial Forge World and Desert World located near the Eye of Terror, it is one of the few locations in the galaxy where the Adeptus Mechanicus stored its tithes of Space Marine gene-seed, in this case of the genetic material drawn from the Imperial Fists Chapter. The planet consisted of only a spaceport and a single large citadel and manufactorum complex known as the Tor Christo. The Tor Christo was a large star-shaped fortress connected to a smaller half-star fortress built into the side of a nearby mountain. The citadel had a large garrison of Imperial Guard troops and even a small Titan Legion to protect its precious contents. During the 13th Black Crusade, this world was assaulted by a large Iron Warriors warband, who successfully defeated the defending Adeptus Mechanicus forces and small Imperial Fists garrison stationed there. When they finally departed, they stole the gene-seed stored within the Tor Christo, a devastating blow to the Imperial Fists, but an insult which would not go unavenged.Medusa (Feral World) - Medusa is the Chapter homeworld of the Iron Hands Chapter of Space Marines. The world of Medusa is a harsh realm of perpetual gloom, situated precariously close to the Eye of Terror in the Segmentum Obscurus. The sun almost never breaks through the dark and polluted sky, as it constantly churns over a land of frozen mountain ranges, interspersed with volcanoes and boiling hot geysers. The landscape is under constant flux, the shifting of tectonic plates forming new mountains and seas, and destroying them as quickly as they are created.Mordian (Hive World) - Mordian is an Imperial Hive World in the Segmentum Obscurus that is the homeworld of the Imperial Guard's Mordian Iron Guard Regiments. Many of the Imperium's enemies have underestimated these ranks of colorfully-uniformed troops, only to find out that they are among the toughest and most uncompromising of the Emperor's soldiers. The people of Mordian are often of a dour and grim temperament, living as they do in perpetual darkness. The suicide rate on the planet is reportedly now the highest in the Imperium since the destruction of the Night Lords Traitor Legion's homeworld of Nostramo. Mordian also once came under a great assault by the forces of Chaos that was defeated only through the extraordinary discipline and valour of the Iron Guard in one of the Imperium's finest moments. Mordian is tidally locked with its star, so that the Mordian day is the same as the Mordian year. As the planet rotates exactly once for every orbit around the sun, one-half of the planet is bathed in perpetual darkness and the other half burnt to a cinder by the glaring sun. This unusual planetological characteristic makes Mordian a truly miserable world to live upon. The planet's lack of rotation prevents any strong winds from developing due to the lack of a Coriolis Effect and as such the atmosphere is thick and dark. The world's billions of human inhabitants live in vast hive cities where all resources are controlled and distributed by the Mordian state. There is much discontent among the people, and the Imperial Guard Regiments raised from Mordian, the Mordian Iron Guard, spend much of their time simply keeping the populace in line when they are not deployed to Imperial war zones.Ran's Eglise - An Artificial World that contributes soldiers to the Astra Militarum.Scintilla (Hive World) - Scintilla is the capital world of the Calixis Sector of the Segmentum Obscurus, and is a thriving Imperial hub that supports the largest planetary population in the sector. It is dominated (some observers say “shared") by two vast hive cities, Hive Sibellus and Hive Tarsus, into which the vast majority of the planet’s groaning population are crammed. Despite the dominance of the two great hives, the “offspring” communities of Ambulon and Gunmetal City contribute significantly to the planet’s economic function. Scintilla is a world of splendours where the wealthy and powerful compete with ruthless appetite. Astonishing magnificence abounds, from the wondrous fashions of the hive nobility to the towering spectacle of the hives themselves. Landmarks like the Lucid Palace and the Cathedral of Illumination are famous throughout the sector.Vostroya (Industrial Hive World) - Vostroya is an Imperial industrial Hive World in the Halo Zone of the Segmentum Obscurus, located beyond the Eye of Terror. The planet is considered an "Industrial World" by the Imperium of Man, because it does not quite meet the legally defined requirements to be considered an Adeptus Mechanicus-ruled Forge World, but it is not quite like an independently-governed Imperial Hive World either. Like all Forge Worlds, Vostroya has deep ties with the Adeptus Mechanicus, but because it is not ruled entirely by the Priesthood of Mars, it is not classified as one of their worlds. The origins of this unusual arrangement can be found in the Age of Strife, when Vostroya was the rare independent world that swore allegiance to Mars, rather than be settled by a colony of Tech-priests as was the norm for almost all of the other Forge Worlds. After declaring its allegiance to the Mechanicus, Vostroya quickly developed into a heavily industrialised world with the influx of Mechanicus personnel and technological knowledge. Under Imperial rule, the output of the many Vostroyan manufactorums now provide war materiel for the Emperor of Mankind's massive war machine.