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The Segmentum Ultima, also known as the Ultima Segmentum, is the segmentum of Imperial space to the galactic east of Terra. The Ultima Segmentum contains the uninhabitable core of the Milky Way Galaxy which is marked by a super-massive black hole.

The Ultima Segmentum is home to the largest number of worlds in the Imperium of Man as it is the largest of the segmentae in terms of its sheer size and spatial volume. It contains the Ultramarines' Realm of Ultramar. It has seen attacks by two separate Tyranid hive fleets, including Hive Fleet Behemoth and Hive Fleet Kraken.

The Eastern Fringe of the galaxy is adjacent to, but not officially a part of the Segmentum Ultima.

This region of the galaxy lies the most distant from the beacon of the Astronomican. Ork empires, pirate conclaves, the expansionist T'au Empire and Tyranid incursions are the main threat within this oft-volatile region of Imperial space.

The Segmentum Fortress of Segmentum Ultima is located on the world of Kar Duniash. It is the site of an Imperial Navy academy and a major orbital shipyard that is the primary builder of the Dominator-class Cruiser.

Since the creation of the Great Rift in the Era Indomitus, approximately half of the Segmentum Ultima now lies on the far side of the rift from Terra, and is part of the Imperium Nihilus where the light of the Astronomican is no longer easily visible to Navigators and other psykers.

Notable Regions[]


The galaxy in the Era Indomitus in the wake of the birth of the Great Rift.

  • Grendl Stars - The Grendl Stars are a constellation of stars located on the far Eastern Fringe of the Milky Way Galaxy that were once known as the Wings of Sanguinius. They are now known to harbour the hyper-violent xenos race called the Barghesi.
  • Ghoul Stars - This region of space is located beyond the furthest reaches of known space, northeast of the Eastern Fringe. This vast tract of relatively unexplored wilderness space was once home to a number of inhabited human worlds. However, an ancient threat, known only as the Pale Wasting in Imperial records, is believed to have been responsible for the destruction of these worlds' populations during the Nova Terra Interregnum. This accounts for the large number of Dead Worlds within the region. The Ghoul Stars region lies beyond the light of the Astronomican, which is used by Imperial Navigators to guide vessels while travelling in the Warp. Without the guidance of this vital beacon, Navigators are unable to sense its guiding light and are forced to navigate blindly. Navigators often refuse to travel into this region for this very reason, for it is extremely hazardous to do so. The Death Spectres Space Marine Chapter currently maintains a constant vigil to ensure that the inhabitants of the Ghoul Stars never again threaten the galaxy.
  • Charadon (Ork Empire) - Charadon is the capital world of the largest and longest-standing Ork empire in the galaxy, also known as Charadon, which is ruled by the tyrannical Ork Warlord Snagrod the Arch-Arsonist, a particularly vicious and sadistic leader of a race noted for its generally vicious and sadistic tendencies.
  • Octarius (Ork Empire) - Octarius is an Ork empire covering the Octarius Sector, an area of space almost as large as the Realm of Ultramar, centred on the Ork World of Octarius. It is ruled by a vicious Ork Warlord known as the Overfiend of Octarius.
  • Sautekh Dynasty - The Sautekh Dynasty is a Necron dynasty consisting of 80 Tomb Worlds. Its Crown World is Mandragora. This powerful Necron dynasty is currently ruled over by Phaeron Imotekh, "the Stormlord."
  • Triplex Sector - The Triplex Sector is dominated by swathes of barren star systems, largely uninhabitable and empty. It is a wasteland of ore-rich asteroids and older, dying stars where a few scattered clans of Abhuman miners and prospectors try to eke out a living. However, it still contains some places of interest to the Imperium in the Eastern Fringe.

Notable Systems[]

  • Baal System - The Baal System is the star system that is home to the world of the same name. Baal is the nominal homeworld of the Blood Angels Chapter of the Adeptus Astartes. Baal itself is a dry, dusty Desert World, scarcely inhabited by anyone other than mutants and feral animals. However its two moons, Baal Prime and Baal Secundus, support notable human settlements and were once "paradises for mortal men" though now they are classified as savage Feral Worlds by the Imperium. Little is known about the past circumstances of these two moons, but at some time in the past (probably during the Dark Age of Technology or the Age of Strife) a cataclysmic conflict arose and led to the widespread use of both viral and nuclear weapons, destroying the ecosystems of both satellites and contaminating their biospheres with radioactive fallout, chemical pollution and biological agents.
  • Badab System - The Badab System is an Imperial star system of the Badab Sector that lies within the Maelstrom Zone of the Segmentum Ultima. With the difficulty of traveling through the region, this area of space has become a haven to pirates, Heretics and Renegades. The Maelstrom Zone is a region of lawless wilderness containing an estimated 20+ Ork empires, numerous Hrud infestations, and countless human pirate strongholds. The Badab System was the heart of the demesne created within the Maelstrom Zone by Lufgt Huron, the Renegade Chapter Master of the Astral Claws Space Marines who bore the infamous title of the Tyrant of Badab. The Badab System served as the heart of Huron's rebellion against the Imperium during the terrible conflict known as the Badab War. Its primary world, Badab Primaris, was finally conquered by the forces of the Loyalist Space Marines in 912.M41 at the cost of all life on that once-thriving Hive World. The fall of Badab Primaris finally brought the terrible internecine conflict to its close.

Notable Worlds[]

  • Charadon - Charadon is the capital world of the largest and longest-standing Ork empire, ruled by the tyrannical Ork Warlord Snagrod the Arch-Arsonist, a particularly vicious and sadistic leader of a race noted for its generally vicious and sadistic tendencies.
  • Dreadhaven - An Artificial World that contributes soldiers to the Astra Militarum.
  • Gorkamorka - Gorkamorka was once an Imperial world known as Angelis. Without warning, a fiery Space Hulk plummeted onto this parched, dead world from the depths of space, its immense impact took just an instant to all but wipe the presence of Mankind from the face of the planet. A pall of radiation and dust was cast over the world that would not settle for an entire decade. Soon the planet's climate and photography was irrevocably shattered and remade in a new and even harsher image. This massive vessel was not uninhabited, as it was occupied by the remnants of a massive Ork WAAAGH! which emerged from the ashes and rebuilt the harsh world in their own brutish image.
  • Kar Duniash - Kar Duniash is the Segmentum Fortress of the Segmentum Ultima as well as the headquarters for the Imperial Navy's massive Battlefeet Ultima. It is also the site of a major Imperial orbital shipyard which is the primary fabricator of the Dominator-class Cruiser.
  • Mandragora - Located along the Eastern Fringe, Mandragora is a Necron Tomb World and crownworld of the Sautekh Dynasty. In ancient times, when the War in Heaven ended, the stasis-crypts of Mandragora were filled to capacity with some of the finest Necron warriors. Since their reawakening from their eons-long slumber, the world of Mandragora has once again become a hub of Necron activity. The Necron Overlord Phaeron Imotekh has dispatched Necron legions to the occupied regions surrounding the Tomb World against Ork Warboss Snagratoof and his Greenskin army.
  • Metalica - A major Forge World of the Imperium of Man.
  • Mu'gulath Bay - Mu'gulath Bay is known as the gateway to the Dovar System, and became a key strategic point for further T'au expansion into Imperial territory. Previously an Imperial Hive World known as Agrellan, the planet was captured by Commander Shadowsun and Ethereal Supreme Aun'va during the Third Sphere Expansion. During the ensuing Battle of Mu'gulath Bay, Tau XV104 Battlesuits proved decisive in defeating the Astra Militarum heavy tanks which guarded the world's capital hive city. The battle to capture the planet was the largest of the Third Sphere Expansion. Shortly after the Prefectia Campaign the Imperium launched a major counterattack against Mu'gulath Bay, determined to reclaim it. In the end the T'au managed to resist, but the Imperium subjected the planet to Exterminatus and destroyed it. Elements of Mu'gulath Bay's T'au population managed to survive thanks to a shield erected by the Earth Caste. The esoteric weapons of the Adeptus Mechanicus proved far more formidable than originally thought by the T'au, however. Mu'gulath Bay had to be abandoned as the entire Damocles Gulf was set ablaze, separating the territory of the Imperium from the T'au Empire. Surviving elements from Mu'gulath Bay attempted to flee to the Farsight Enclaves, but were set upon by Commander Surestrike at the order of the Ethereals. Surestrike managed to destroy most of the rebel T'au, but some managed to escape.
  • Ohmn-Mat - Once a Forge World of the Adeptus Mechanicus, the burning grave of Ohmn-Mat is a well-known sight within the Ultima Segmentum. The Forge World descended into civil war at the outbreak of the Horus Heresy, and both factions were reinforced by contingents of Legiones Astartes before the war escalated and led one or both factions to ignite Ohmn-Mat’s atmosphere. All forge-fanes where destroyed by secondary atomantic explosions, further shrouding the planet in fire. The fires still rage to this day.
  • Orask - At the very edge of the Iquathan Deeps in the northern Ultima Segmentum, near the border of the Ghoul Stars, sits the Sentinel World of Orask. In recent times, a terrible assault occurred in 977.M41, when a splinter of the Eastern Hive Fleets of the Tyranid menace appeared, disoriented and twisted by its passage through the Ghoul Stars, and fell on the Orask System like a ravenous beast. A great battle ensued, that proved brief but bloody. The stoic defenders of Orask were backed by a full company of the Red Talons Space Marine Chapter and a Titan maniple from the Legio Magna. Despite horrific casualties in the tens of thousands sustained within a matter of mere days, the valiant defenders were able to push back their monstrous attackers. Eventually they contained the threat and purged the vile xenos from Orask's blasted surface. Evidence persists that some harbinger organisms escaped to the outer systems.
  • Pavonis - A troubled industrialised Hive World located on the Eastern Fringe. The Ultramarines 4th Company under the command of Captain Uriel Ventris was sent to quell the troubles caused by humans and xenos alike. A secret, heretical organisation, known as the Church of the Ancient Ways, plagued the planet with random bombs planted around the various manufactorums. In addition, the world was also continuously raided by Dark Eldar corsairs over the course of six years. Uriel Ventris was successful in defeating both the civil insurrection as well as crushing the Dark Eldar and their human collaborator in the hidden tomb of the C'tan Shard known as the Nightbringer. Unfortunately, this vile entity escaped the confines of its tomb and fled into the galaxy at large. After completing a Death Oath and being cleared of taint, Uriel Ventris was reinstated as the commander of the 4th Company. He was then given the opportunity to prove himself in the eyes of those who still doubted him by returning to the world of Pavonis and defending it from T'au invaders.
  • Prefectia - Prefectia was the site of the Prefectia Campaign fought between the T'au Empire and the Imperium.
  • Pythos - Pythos is an Imperial Death World, covered mainly in dense jungles, with occasional areas of scorched grassland. Its jungles and oceans are inhabited by massive saurian predators. Because of the dangers of moving through the lowlands and across the oceans, the human settlers of Pythos settled in mountaintop mining colonies. From these, they derived a precarious and meagre existence mining the precious minerals found in the planet's mountain chains. Hundreds of these strongholds were scattered over the planet, each home to populations of only a few thousand Imperial citizens. Pythos' only major city is the Hive-port of Atika, located on the coast of the planet's largest ocean, and surrounded on its landward side by the aptly-named "deathglades." Atika was a small spire city with its main habitation zones located in its dome-like upper levels, high above the surrounding swamplands. Travel between Atika and the delver-strongholds was carried out in dilapidated lighter-than-air dirigibles known as "sky barges," lumbering through the skies high above the ferocious creatures that inhabited the lowlands in relative safety. It was a major source of the fighting during the Pandorax Campaign and was home to the prison for daemons known as the Damnation Cache.
  • Radnar - An Imperial hive-world near Ichar IV. Infested with Tyranids during the Hive Fleet Kraken incursion, an Imperial Guard Emperor's Shield Regiment used its Armoured Company to destroy them and their nests around Jourmall Hive.
  • Tarsis Ultra - Tarsis Ultra is an Imperial Dead World that was formally a Civilised World. It was unique, in that it also possessed certain features of a classic Agri-World, since it was able to produce food for other Imperial worlds within the Ultima Segmentum. Despite its status as a major exporter of food, the planet suffered from long, harsh winters that gave it the appearance of an Ice World. The world was the site of a great battle between the Ultramarines Space Marine Chapter and the Tyranids of Hive Fleet Leviathan in 999.M41. This conflict left a terrible mark upon the world, but a worse fate befall Tarsis Ultra when it was finally transformed into an uninhabitable Dead World by the actions of the Iron Warriors Warsmith Honsou, who unleashed a terrible biological weapon known as the Heraclitus Virus into Tarsis Ultra's Tyranid-altered biosphere.

Notable Celestial Bodies[]

  • Storm of the Emperor's Wrath - A notable and fiercely persistent Warp Storm which has raged since the Age of Apostasy and is believed by the Ecclesiarchy to have been created by the Emperor Himself to indicate his displeasure with the attempt of the renegade High Lord of Terra Goge Vandire to seize control of the Imperium in the 36th Millennium.
  • Maelstrom - The Maelstrom is a massive and ancient Warp Rift located near the galactic core. This area of space is riven with Warp Storms so intense that stellar travel in the region is virtually impossible. Second only to the great Warp Rift that is the Eye of Terror in the Segmentum Obscurus, the Maelstrom scars both the physical universe and the fabric of the Immaterium beyond. This volatile region of space has become a haven to pirates, criminals and renegades such as the Red Corsairs Chaos Space Marines as well as gateways to the Dark Eldar's Webway city of Commorragh, who use it as a base from which to launch raids on Imperial space.
  • Ymga Monolith - The Ymga Monolith is a mysterious structure located in the Attila System of Segmentum Ultima. The monolith lies on the edge of the territory claimed by the Necron Sautekh Dynasty. The Eldar maintain a Webway portal close to the Monolith, denoting its location with the same rune used to mark the location of the Hadex Anomaly. It is said that in the early Great Crusade, one of the Lost Primarchs led an expedition to the Ymga Monolith. What he found there is not known. The Monolith's true nature became clear in the aftermath of the Great Rift's creation, during the 13th Black Crusade, as it began to glow when the growing Warp Storm known as Cerberax neared its location. This caused a perfect sphere of order untouched by Cerberax's progress across the stars; causing the Adeptus Mechanicus' Holy Requisitioners to discover the Monolith was in fact a Necron phase node of immense potency. This was later proved to be true, when the Necron warships of the Sautekh Dynasty arrived to defend the Ymga Monolith and began to clash with daemons of Khorne who had emerged from the Cerberax Warp Storm. This conflict has become known as the Cerberax Wars and the Ymga Monolith plays an important role in bolstering the Sautekh forces as visions from the Imperium's Corinthe Mind-Scryers show that the Monolith is somehow physically duplicating every Necron starship that makes contact with it.

Other Places of Interest[]

  • Craftworld Iyanden - The Iyanden Craftworld was once one of the largest and most prosperous of all the remaining Asuryani craftworlds. They barely survived an attack by the Tyranid Hive Fleet Kraken, which nearly destroyed the Craftworld and killed four-fifths of its population. On the verge of total annihilation, Iyanden was saved from complete destruction by the exiled Prince Yriel, who had formerly been the High Admiral of the Iyanden fleet. Yriel and his exile Asuryani pirate raiders, even though previously vowing never to return to Iyanden, could not bear to have their craftworld destroyed and launched an attack on the Tyranid fleet. Taking the final battle to the craftworld itself, Yriel used an ancient artefact spear called the Spear of Twilight to slay the Hive Tyrant that led the assault. In doing so, Yriel doomed himself to a slow and painful death due to the psychic artefact being bound to its user and slowly burning away their soul. For now, however, the forceshield worn by Yriel staves off the constant negative energies of the Spear. Regardless of his actions, the chances of Iyanden recovering from its losses against the Tyranids were slim and their future looked bleak. Iyanden's name means "light in the Darkness" in the Aeldari Lexicon and its chosen colours are gold and blue. The Iyanden Craftworld can usually be located in the galactic southeast in Ultima Segmentum and is one of the two Asuryani craftworlds found near the borders of the T'au Empire, the other being Alaitoc.


  • Chapter Approved 2003, pg. 74
  • Chapter Approved 2004, pg. 19
  • Codex: Blood Angels (5th Edition)
  • Codex: Deathwatch (7th Edition) (Digital Edition), "The Heraldry of the Honoured"
  • Codex: Necrons (5th Edition), pg. 14
  • Gorkamorka: Da Uvver Book, pp. 5-10, 103-1058
  • Gorkamorka: Digganob, pp. 6-8, 29, 57
  • Gorkamorka: Gubbinz, "Da Necron Rayd", pp. 13–15
  • Index Astartes I, "White Scars"
  • Index Astartes II, "Angels of Death: The Blood Angels"
  • Index Astartes IV, "The Salamanders"
  • Codex: Imperial Guard (5th Edition), pg. 27
  • Codex: Necrons (5th Edition), pg. 14
  • Codex: Space Marines (5th Edition), pp. 49-50 (Map)
  • Codex: T'au Empire (8th Edition) pp. 37-38
  • Codex: Tau Empire (6th Edition), pp. 32-34, 53
  • War Zone Damocles: Kauyon (7th Edition), pg. 119
  • Codex: Tyranids (5th Edition), pp. 28-31
  • Codex: Tyranids (4th Edition), pg. 21
  • Codex: Ultramarines (2nd Edition)
  • Commissar Cain (Book Series) by Sandy Mitchell
  • Fabius Bile: Clonelord (Novel) by Josh Reynolds, Ch. 18
  • Gathering Storm - Part II - Fracture of Biel-Tan, "Chapter 1: The Dance of Destiny - Addenda Inquisitoria" (sidebar)
  • Imperial Armour Volume Nine - The Badab War - Part One
  • Imperial Armour Volume Ten - The Badab War - Part Two
  • Nightbringer (Novel) by Graham McNeill
  • Planetstrike (5th Edition), pp. 57-59
  • Courage and Honour (Novel) by Graham McNeill
  • Tome of Fire (Novel) by Nick Kyme
  • The Damnation of Pythos (Novel) by David Annandale, Chs. 1-12
  • The Horus Heresy Book Six: Retribution (Forge World Series) by Alan Bligh, pp. 29-30
  • Spear of the Emperor (Novel) by Aaron Dembski-Bowden, Chs. 3-5, 10, 17, 22, "Proem - The Historian III"
  • Warhammer 40,000: Apocalypse
  • Warhammer 40,000 Chapter Approved - The Book of the Astronomican
  • Warhammer 40,000: Compendium, "The Badab War", pp. 33-35
  • Warhammer 40,000: Rulebook (5th Edition), pp. 117, 138
  • Warhammer 40,000: Rulebook (4th Edition), pg. 91
  • Warhammer 40,000: Rulebook (3rd Edition), pg. 278
  • Warhammer 40,000: Rogue Trader (1st Edition)
  • White Dwarf 101 (UK), "Index Astartes: The Badab Uprising" by Rick Priestley
  • White Dwarf 139 (US), "Space Fleet: Rules Expansion", pp. 8-36
  • White Dwarf 140 (US), "Space Fleet: Additional Background, Rules, Data Cards and Counters", pp. 46-75
  • White Dwarf 329 (US), pg. 76
  • White Dwarf 460 (January 2021), pp. 38-40
  • Rogue Trader: Core Rulebook (RPG), pg. 305
Segmentum of the Known Galaxy
Segmentum Solar Segmentum Ultima Segmentum Tempestus Segmentum Obscurus Segmentum Pacificus