Planets of Warhammer 40,000

This is an incomplete list of the more notable planets in the Warhammer 40,000 universe. No full list could ever be compiled because the Imperium of Man consists of over a million worlds, with many more planets populated by various alien species like the Eldar and the Orks.

Types of Planets
The Imperium of Man is home to over one million human-settled planets scattered across over 100,000 light years of space in the Milky Way Galaxy. Most of these worlds were settled many centuries before the Great Crusade of the 31st Millennium reunited the human colony planets of the galaxy beneath the rulership of the Emperor of Mankind, though thousands more have been settled in the ten millennia since by Imperial colonists. The Adeptus Administratum of the Imperium generally classifies all planets in the galaxy according to several different criteria to produce a standard classification system that makes it simple to assign the proper tithe grade for the amounts of economic resources or recruits for the Imperial Guard that will be drawn from the world for wider Imperial use, if any.

Accatran
This Forge World is the homeworld of the Adeptus Mechanicus' Legio Destructor Titan Legion, also known as the Beasts of Steel. The planet is located in the Ultima Segmentum.

Aerius
A hive world of great importance to the Imperium, it suffered a devastating plague when the Balestar, a comet appearing every two thousand years, returned. The plague was connected with the enigmatic Black Pyramid, an impenetrable Eldar structure which was built, unknown to the local human population, to restrain a Greater Daemon of Nurgle called Botchulaz.

Adrantis Five
Adrantis Five was a human-settled, extremely technologically advanced planet which had been separated from the Imperium of Man for over five thousand years. It was conquered by Lord Commander Solar Macharius during the Macharian Crusade in the Segmentum Pacificus. The planet's population were technologically very advanced, and when Macharius arrived he said that they had 'turned to the dark certainties of science, and created many new and wondrous machines.' Even so, Macharius still had to conquer it. He was held at bay for two years until the planet finally succumbed to a redirected comet. 'Of its secrets, nothing now remains' were the last words of Macharius on the subject.

Agripinaa
Agripinaa is an Imperial hive world where virtually the entire surface of the planet is covered with industrialized infrastructure, piplines, factories, mines, refineries, processing plants, and manufactorum cathedrals. Like most other planets in its sector, this world primarily provides materials for the Cadian front and its industrial heartland is soley engaged in the production of ammunition. Its hives are sealed due to a toxic atmosphere from pollution. Agripinaa is located in the Ultima Segmentum near the Eye of Terror and was involved in the fighting of the 13th Black Crusade. Agripinaa did not survive an assault by the Forces of Chaos well and much of her industrial heartland was laid ruin.

Anark Zeta
Anark Zeta is a feral world that is one source of the Abhuman troops known as Ogryn for the Imperial Guard. The world is very cold and has extremely high gravity, hence the development of the Ogryn population. The surface of Anark Zeta is barren with no known cities. The only inhabitants of this frigid world are the large Abhumans know as the Ogryn. The Ogryn live in nomadic hunter-gatherer tribes but when the Imperial Guard needs new Ogryn troops, Guard recruiters come to Anark Zeta to promise the dim-witted Ogryns all that they can eat if they will serve the Imperium as its powerful shock troopers.

Angelis
Known to the Orks as "Gorkamorka". This planet is located in the north of the Eastern Fringe. There is also considerable evidence that there could be, or was a Necron presence on the world. There are also theories that it is still a Necron tomb world.

Armageddon
A hive world that has been repeatedly invaded by the Orks, where the outdoors are nothing but huge wastelands so polluted and hostile they can kill a man in a day. Due to this, all infantry always wear gas masks, trench coats and rebreather units whenever outside. Additionally, this causes its famed Steel Legion regiments to field large numbers of mechanized infantry borne by Chimera IFVs, of which Armageddon is also famed for producing.

True to its name, Armageddon has been the site of three massive wars in the history of the Imperium during the 41st Millennium. The First War for Armageddon was an invasion by the Chaos forces of the Daemon Primarch Angron of the World Eaters and most recently a pair of invasions during the Second War for Armageddon and the Third War for Armageddon by the Ork Warlord Ghazghkull Mag Uruk Thraka. As a result, the people of Armageddon are a tough lot, and its armies experienced in fighting the Orks. Armageddon is a Mecca of sorts to all Orks in the region, who refer to the planet as 'Armour-get-em'. As such, Orks are constantly pouring into the system to join the ongoing battle. Orks 'native' to Armageddon are considerably tougher than normal Orks; Orks thrive in combat situations, becoming stronger, tougher and more aggressive with each generation to match and eventually best their opposition.

Artemis
An Imperial world that was under heavy attack by Chaos, including their own warped Titans. Also the site of a massive Warp/Realspace overlay, which spawned a daemon so huge it was literally several dozen times larger than even an Emperor class Titan.

Arthas-Moloch
A Dead World discovered by O'Shovah, where he found the Dawn Blade; the Tau call it an "Artifact World."

Baal
Baal is the nominal homeworld of the Blood Angels chapter of the Adeptus Astartes. Baal itself is a dry, dusty and largely uninhabitable desert world, but its two moons, Baal Prime and Baal Secundus support notable human settlements and were once "Paradises for mortal men". Little is known about the past circumstances of these two moons, but at some time in the past (probably during the Age of Strife) a cataclysmic conflict arose and led to the widespread use of weapons of mass destruction, destroying the ecosystems of both satellites and contaminating their biospheres with radioactive fallout, chemical pollution and biological agents.

The indigenous peoples of Baal Prime and Baal Secundus suffered greatly and gradually became degenerate, mutated and sickly, the survivors banding together into semi-nomadic tribes. These tribespeople appear to have maintained some technology as mention is made of rad-counters, rad-suits (self-evidently advanced technological equipment to protect from the effects of radiation), vehicular transport and advanced weaponry. Many tribes turned to cannibalism and became even further corrupted by the toxins endemic to their environment, but at least one tribe maintained a noble and enlightened outlook; known as the 'Ones of Pure Blood', often contracted simply to 'The Blood'. It was The Blood who encountered the infant Primarch Sanguinius when he came to rest on Baal Secundus, and they adopted him as one of their own. The tribespeople were astonished at the young Primarch's rate of growth, constitution and strength, and he soon became a hero among them, on at least one occasion defending The Blood against an attack by another, mutant tribe, and killing many of them. It was in this capacity that he was discovered by the Emperor during the Great Crusade. Sanguinius instantly recognised the master of mankind and swore fealty to him, taking command of the Blood Angels legion created from his own genes. The Legion made Baal Secundus its home and base of operations as it has been ever since.

Baal Secundus is the site of the Blood Angels' fortress monastery, about which little is known.

Bakka Triumveron
Bakka Triumveron is a titanic gas giant far bigger than the Solar System's Jupiter. Bakka's outlying moons however are habitable, each one roughly the size of Terra and all of them heavily populated. These include Rogelin, Sanctuary, Half Hope and Grey Harbour. The Bakka system is one of the most populated in Segmentum Tempestus. Bakka is the Fleet Headquarters of Segmentum Tempestus. (The Horus Heresy: Battle for the Abyss, p. 183)

Belis Corona
Belis Corona is an Imperial Dead World located near the Eye of Terror, serving as the Segmentum Obscurus' primary Imperial Naval base. It has a vast conglomeration of orbital dockyards orbiting it, where entire sector battlefleets can be serviced. Munitions stockpiles are stored in armoured bunkers buried many kilometres below the planet's surface. Belis Corona was heavily involved in the battles of the 13th Black Crusade.

Besarife
Besarife is a planet in the furthest outreaches of the Segmentum Tempestus. It is slightly smaller than Terra, it shares a near-identical atmosphere. The planet is best characterized by its deep forests of exotic trees not seen anywhere else in the Segmentum. Besarife is tilted on its axis by a mere 3.5 degrees and has some seasonal weather patterns such as light hurricanes and snow storms. The northern and southern poles are extremely arid and host a low survivability rate.

The planet was first explored after the Horus Heresy ended by Space Marines of the surviving Legions. After the chapter of the Hymn Knights was born, it took residents on the sparsely populated planet and began building their defences.

Beta Anphelion IV
Beta Anphelion IV is the second moon of the fourth planet in the Anphelion System. It was the focus for Forge World's fourth major work, Imperial Armour Volume 4: The Anphelion Project which described the investigation by an Ordo Xenos Inquisitor of a secret project related to the Tyranids in the year 850.M41.

Black Reach
Black Reach is the Hive World fought over in the Warhammer 40,000 Beginners Boxset 'Assault on Black Reach'. The Planet was invaded by Zanzag's Orks in 855 M41. Zanzag was defeated by Captain Sicarius and the Ultramarines 2nd Company.

Brontissa
A planet that was invaded by the Tyranids. Imperius Dictatio had in its past joined the fray and participated in eight straight days of intense fighting. On the ninth, all Imperial forces were pulled out into space, and the planet virus bombed.

Cadia
Cadia is a Fortress world which guards the entrance to the Eye of Terror. Cadia has endured many attacks from the Forces of Chaos and the Chaos Traitor Legions and several Black Crusades. Cadia is highly militaristic; birth rate and recruitment rate are synonymous. During the 13th Black Crusade in 999.M41 Cadia was attacked by a Blackstone Fortress controlled by the Chaos Warmaster Abaddon the Despoiler. Cadia is also very well known for its elite Cadian Shock Troop Regiments -- men and women raised from birth to defend the Cadian Gate.

Caliban
Once the homeworld of the Dark Angels chapter, Caliban was destroyed during a heresy on the planet. Now all that remains is an asteroid field and The Rock, the mobile fortress-monastery of the Dark Angels. Before its destruction, Caliban had an extremely harsh environment. Vast, impenetrable jungle covered all of the planet's surface, with monstrous Chaos creatures haunting them. The human population formed into several Knightly orders, to fight off the hordes, as a lone human would be killed in a minute. It is amazing how the Dark Angels Primarch Lion El'Jonson ever survived as long as he did there.

Calth
As part of Ultramar, an area under the jurisdiction of the Ultramarines, Calth provides recruits for the Ultramarines Chapter. The aspirants compete in a series of contests between hopefuls to determine who is worthy of joining the Space Marines. Calth's inhabitants live in subterranean cities where the deadly light of Calth's blue sun cannot reach them. The caverns of Calth are constructed on such a huge scale, and with such grandeur, that they are as light and airy as any city of Macragge. The world above is devoid of air, the atmosphere stripped away during the Horus Heresy, when the Ultramarines and the traitorous Word Bearers, under the command of Kor Phaeron and Erebus the Dark Apostle, came into conflict.

Although the inhabitants are perfectly capable of living on what is grown in nutrient vats, they prefer to import foodstuffs from Iax. The shipyards of Calth also earn the world a name to look up to, their vessels used by the Ultramarines and the Imperium at large.

The Ultramarines captain Uriel Ventris was born upon Calth. The Tyranid "character" Old One Eye was discovered on Calth in icepacks. At least one regiment of the Imperial Guard has been raised on Calth.

Catachan
Catachan is a death world almost entirely covered in dense jungle. Vegetation on Catachan reacts to attempts at colonization and rapidly grows back whenever it is cleared. This forces the population of the planet to live a semi-nomadic existence, moving on whenever the jungle violently reclaims their land. It is believed that all of Catachan's native fauna is carnivorous, as is much of the flora. Poisonous creatures are extremely common. The most well known of Catachan's native animals is the infamous Catachan Devil, a voracious predator somewhat similar in appearance to an enormous scorpion. Devils can grow over 40 paces long, but their bulk and lack of speed allow many creatures to simply avoid them. One of the most dangerous animals on the planet is the Catachan Barking Toad, a seemingly innocuous-looking creature which discourages predators by exploding and spraying a highly lethal acidic toxin on anything nearby. The largest of the species, the Greater Catachan Barking Toad, is rumoured to be capable of annihilating everything within a half-kilometer radius upon detonation. The dangers in Catachan's jungles are not limited to the fauna; in many cases the plant life can be just as deadly. The Spiker, for example, is a plant capable of firing extremely sharp spikes into the bodies of its victims, which then emit a mutative chemical which eventually turns the unfortunate recipient into another Spiker. The Brain Leaf is an example of the more insidious dangers to be found on Catachan. The brain leaf has long, smooth tendrils, at the end of each of which is a single leaf. The plant can attach these leaves to living creatures, taking control of their nervous systems and using them as protection and, eventually, compost. Insects and diseases are every bit as dangerous as the larger monsters. Blood-wasps are swarming, carnivorous insects that will swarm over a man and eat him down to a skeleton in a matter of hours. Another subtle threat are Heretic-ants, highly venomous ants so named because they attack their victims from the feet - going for your soles (souls, so to speak). Creatures native to Catachan are often found elsewhere in the Imperium (the brain leaf can also be found on Necromunda, for example). Sometimes they are exported deliberately, and sometimes they are simply unwitting stowaways on board transport vessels. Catachan only has one export for the greater Imperium: Its people. Those born on Catachan are, unsurprisingly, of hardy stock, and the regiments of Catachan Jungle Fighters raised from the planet are among the Imperium's best guerrilla fighters.

Chaeronia
The planet featured in Dark Adeptus (Grey Knights 2) by Ben Counter. A former Forge World, it was taken into the Warp for over 1000 years warp-time, while only 100 years in real-time. It is ruled by the Dark Mechanicus, although there are still a few loyal Adeptus Mechanicus troops. It contained an STC Titan, which was destroyed by the Grey Knights. It is likely that the planet was destroyed by Exterminatus due to the extent of tech-heresy that encompassed the entire planet.

Cypra Mundi
Cypra Mundi is an Imperial Forge World and Naval Base of Segmentum Obscurus, the sector including the Eye of Terror. Cypra Mundi is located on the Northern fringe of the galaxy. During the 13th Crusade, a massive fleet was dispatched from Cypra Mundi to reinforce the Imperial Navy, which had been fighting an ongoing battle against the seemingly endless waves of Chaos vessels. The fleet from Cypra Mundi staged at Belis Corona in preparation for a massive counter-push into the Cadian Gate, just outside the Eye of Terror. Cypra Mundi is also the traditional home of Naval officers in the Segmentum, which are chosen from the aristocracy of Cypra Mundi

Cyrene
Located in Sub-Sector Aurelia, it is a planet visited extensively by the Blood Ravens to recruit new members. When the Blood Ravens' 3rd company commander Gabriel Angelos, himself a native of Cyrene, returned to his homeworld to conduct the Blood Trials to induct new recruits, he found evidence of wide-spread heresy and mutation among the populace. He quickly sent a coded message to the Inquisition, who performed Exterminatus on the world.

Davin
Davin is the prime world of the solar system of the same name, conquered during the Great Crusade by Warmaster Horus and his 63rd Expeditionary Fleet. Davin is one of two habitable worlds in its star system, the other is its moon. Both Davin and its moon were desert worlds discovered in the 140th year of the Great Crusade, where the Primarch Horus' 63rd Expeditionary Fleet linked up with a lost strand of humanity on the surface of the planet. It was the eighth world conquered by that fleet of the Great Crusade, and so for a time Davin had the designation Sixty-Three Eight. It is principally known for being the world on which Horus made his pact with the Ruinous Powers of Chaos and so began the |Horus Horus Heresy. This event took place in the Temple of the Serpent Lodge, an establishment secretly devoted to Chaos Undivided, where he was treated for injuries incurred while quashing a rebellious force on Davin's moon.

Dolumar IV
Dolumar IV is the planet fought over in the PC game Fire Warrior. The planet was a small, but growing world, until Imperial forces attacked a nearby Tau world, killing many Tau and kidnapping the Etherea Ko'vash. Tracking the imperials back to Dolumar IV, the Tau attacked in force. The battle on and over the planet would be the Trial by Fire of a young Fire Warrior named La'Kais, who would prove instrumental in stopping the demon Tarkh'ax. To cleanse the taint of Chaos, the planet was subjected to Exterminatus.

Dynikas V
Dynikas V, a world that is part of a star system in the Ghoul Stars region, was an ocean world with few island land masses that was home to a small human colony. It was eventually overran by the remnants of a splinter Tyranid Hive Fleet and was considered a Dead World, with an extremely toxic aquatic environment. The Traitor Apothecary Fabius Bile used the world as the home of one of his facilities. Bile's base was attacked by a combined force of Blood Angels and Flesh Tearers Space Marines, and in the process, was also overrun by the Tyranids. The planet was subsequently subjected to Orbital Bombardment by the Space Marine cruisers Tycho and Gabriel and turned into a smouldering rock devoid of any life or use.

Etiamnum III
This airless, barren planet was home to a small community of hermits who for millennia had lived out a simple life of contemplation and study in a reclusium. This was shattered when the Thousand Sons Sorcerer Mordant Hex attacked and vented some of the beguiled and strangely calm hermits into the airless atmosphere. The Thousand Sons then penetrated deep into the mountain fortress with little resistance on a hunt for something. The planet had held a deep secret, a long forgotten webway portal which Ahriman then used to gain entrance to the webway in Abaddon’s 13th Black Crusade. After the Campaign ended, Ahriman was ejected from the Webway and the webway gate permanently sealed.

Eustis Majorus
Eustis Majorus is a hive world in the Anjellus sub-sector that features in the Ravenor novels by Dan Abnett. Its capital is the hive city of Petropolis, a dirty, polluted and overcrowded city that was in fact designed as a huge "Psychic Resonator" by the infamous heretical architect Theodor Cadizky with precisely nine hundred and ninety-nine temples, the central one of which, called the Old Sacristy, being in the exact centre of the hive, with all of the others, the axial temples, forming lines from the Old Sacristy that give the entire hive an overall mathematical symmetry.

Fenris
Fenris is a cold, icy Death World in the Segmentum Solar that is the homeworld and primary recruiting ground of the Space Wolves. The planet's culture is made almost entirely of scattered tribes similar to Viking Age Scandinavia. The Space Wolves keep a close watch over the people of the world, recruiting fallen warriors who have proved their valour in battle much like the Valkyries of Norse legend. The Space Wolves' fortress-monastery is called the Fang, a massive citadel built atop the tallest mountain of the only stable continent on the world, Asaheim. The Fang is the home base of the Space Wolves and extends into the surrounding mountain range as well as into orbit, drawing energy from the geothermic source of the planet's core. The complex includes huge ground-based anti-ship orbital defence weapons concealed as nearby peaks, docks at the summit for the Space Wolves' battle barges and strike cruisers, numerous shrines to the Emperor along the lower slopes, and massive fusion and geothermal reactors deep underground. Outside of Terra itself, the Fang is considered one of the most impregnable fortresses in the galaxy. It has never been conquered, although the Thousand Sons Traitor Legion did manage to briefly occupy the outer slopes of the Fang after luring the bulk of the Space Wolves' forces away.

Fortis Binary
Fortis Binary was formerly a Mechanicus Forge World, and it featured in the Imperial Guard novel written by Dan Abnett called the First And Only. A Chaos uprising by a group of former workers called the Shriven led to a long, drawn-out conflict of trench warfare between the Chaos Cultists and the Imperial Guard for control of the planet.

Galt
Technically Galt Three in the eponymous system, it has an elliptical orbit about a yellow sun and is characterised by three main continents and dense jungle growth. Their most common export to the Imperium is the bud of the red lotus used in many alchemical products. It houses a pre-Imperial structure known as the Temple of Xikar, home to a sect known as the Brothers of Perpetual Bliss. The Temple and planet were devastated in an Ork raid led by one Ork Warlord, Gurg, who possessed one-third of the Talisman of Lykos, which made him practically invulnerable.

Golgotha
A Squat homeworld. In 3rd edition, the Squat homeworlds were supposedly destroyed by the Tyranids. Golgotha was previously attacked by Ghazghkull Thraka and was the origin world of the Ordinatus Golgotha.

Gravalax
Mainly mentioned in the novel "Ciaphas Cain: Hero of the Imperium" the Imperium held colonies on this planet with the Tau and "Xeno-Lovers" a group of pro-tau humans who fight the PDF and the Valhallan 597th Guard regiment. Not much history is told about this "miserable mud-ball." The combined forces of the Valhallan 597th and Commissar Cain, and an Inquisitor of the Ordo Xenos, Amberley Vail, were sorely tested on Gravalax. After political instability caused the fall of the Tau's peaceful diplomatic missions and the Order to eliminate the human planetary governor by Lord General Zyvan. This was all dwarfed by the invasion of one of the first Tyranid hive fleets in many a century.

Gryphonne III
Gryphone III was once a beautiful planet, though it was destroyed after the Great War. It was once the homeworld of the Avengers Chapter, and before the planetary destruction the Avengers acted quickly enough to move all their knowledge on to their spaceborne mobile fortress-monastery. The exact location of this planet is unknown, but it is rumoured that some lost knowledge or important artefact that belonged to the Imperium remains hidden on the world.

Gudrun
Located in the Helican sub-sector of Segmentum Obscurus it is a relatively idyllic world with stately manors controlling vast estates of rolling green hills studded with small villages. A feudal world controlled by rival Great Houses. Once the Capital of the Helican sub-sector, it is no longer, the centre of government having been moved to Thracian Primaris. It is not dissimilar to ideas of 'Merry Olde England'. For a time it was the home and headquarters of the Inquisitor Gregor Eisenhorn as detailed in the novel, Malleus, by Dan Abnett.

Hagia
Located in the Sabbat Worlds, Segmentum Pacificus. It is the birthplace of Saint Sabbat, and the location of her remains. During the Sabbat Worlds Crusade the forces of Chaos attacked the world and mocked the people of the world by calling themselves Infardi which was the local word for Pilgrim. Colonel-Commissar Ibram Gaunt and his regiment the Tanith First and Only fought the Infardi in the capital city of the world, Holy Doctrinopolis, and drove them out but at a very heavy cost. To redeem himself and his regiment, Gaunt led an honour guard to the Shrinehold of Saint Sabbat to safeguard the relics there from the incoming Chaos Fleet.

Herodor
A desolate world, located in the Sabbat Worlds, Herodor was the planet where the Imperial Saint Sabbat was believed to have been reincarnated, providing a major morale boost to the forces of the Imperial Sabbat Worlds Crusade. It was attacked by the forces of Chaos, mostly members of the Blood Pact but also with the aid of nine Champions of that foul creed. Eventually, Imperial forces including the Tanith First Imperial Guard Regiment of Gaunt's Ghosts fame aided in crushing the Chaos invasion.

Hubris
Hubris was named for the excessive pride of the colonists who founded a society there despite the harsh climate which sees the planet icebound for 11 months of the 29 month Lunar Cycle. This period is known locally as Dormant and the majority of the population enters cryogenic stasis in hibernation tombs to escape the cold. This is followed by Thaw, a period of feasting and activity designed to help overcome the effects of cryosleep and Vital, the normal active time of the planet. In the novel Xenos, it was on this planet that Inquisitor Gregor Eisenhorn killed the heretic Murdin Eyclone, who was attempting the bodily resurrection of the infamous Pontius Glaw with the mass murder of cryosleepers. It was this event that started the chain of events that marked Eisenhorn's slide into radicalism.

Hydraphur
Hydraphur is a hive world located in the Segmentum Pacificus. It is the location for the main Imperial Navy battlefleet headquarters in its sector. Hydraphur is a prime recruiting ground for the Imperial Navy, with many of the prominent families on Hydraphur being connected to the Imperial Navy and various Rogue Trader houses. As a result of the influence of the Rogue Traders, Hydraphur is a commercial and manufacturing hub for the Imperium of Mankind and a person's financial connections are as important as their familiar one. This has lead to the Hydraphuran convention of adopting both a clan name (the business you are affiliated with) and a family surname (for example Lord Kalfus-Medell is a Lord of the Medell family, affiliated with the Kalfus clan). In addition to the Imperial Navy, the Ecclesiarchy and the Adeptus Mechanicus have strong interests and ties to Hydraphur. Law is enforced (as on most Loyalist Imperial worlds) by the Adeptus Arbites.

Ichar IV
Ichar IV is an Imperial hive world located in the Ultima Segmentum, to the galactic north of the Realm of Ultramar. It is a vital industrial centre for the region, producing supplies for many armies. The planet's major exports include ore and mycoproteins. During the Second Tyrannic War, the planet was taken over by a Genestealer Cult that was ultimately defeated by the combined forces of the Inquisition, the Ultramarines, the Imperial Guard and Planetary Defence Forces.

Istvaan III
See the Istvaan III section under Horus Heresy for more details.

Istvaan III was an Imperial hive world whose inhabitants rebelled against the Imperium during the final days of the Great Crusade. When Warmaster Horus and elements of the Sons of Horus, the Emperor's Children (with their Primarch elsewhere the Emperor's Children were led by Lord Commander Eidolon), the Death Guard and the World Eaters Legions reached Istvaan III, there were no negotiations; instead, Horus sent an assault force against the planet's vital areas, where the leadership of the planet would most likely be hiding. This, however, was actually a trap for those Space Marines laid by Horus to purge the Traitor Legions of their remaining Loyalists, which had all but declared their loyalty to Horus in his mad bid to overthrow the Emperor of Mankind. The Warmaster ordered the planet virus-bombed in order to kill any remaining resistance, and then with the words "Let the galaxy burn", ignited the gases given off by the massive organic decomposition that resulted from the actions of the virus upon the bodies of the planet's 12 billion people. However, the Loyalists were belatedly warned of the virus-bombing by Captain Saul Tarvitz of the Emperor's Children and several hundred managed to survive the castastrophe. These Space Marines put up a heroic defense against the Traitor Legions' attempt to destroy them for three months before finally succumbing to an orbital bombardment. However, the Battle of Istvaan III had caused major losses for the Traitor Legions and dramatically slowed down their timetable, ultimately contributing to their defeat during the Siege of the Imperial Palace on Terra. After the end of the battle, Horus next moved his forces to the nearby world of Istvaan V for a showdown with the Loyalist Legions.

Istvaan V
See the The Drop Site Massacre section under Horus Heresy for more details.

Istvaan V was where the Traitor Legions of Warmaster Horus redeployed following the virus-bombing of Istvaan III. Upon learning of the terrible atrocity Horus had committed, the Emperor deployed seven Legions to bring Horus to account for his actions. The Iron Hands, Salamanders and Raven Guard made up the first wave of the attack, but were pushed back by the superior tactics of Horus' maddened followers. The reserves were called in, but the four Legions comprising the reinforcements - the Iron Warriors, the Alpha Legion, the Word Bearers and the Night Lords - had betrayed the Emperor and were prepared to follow Horus. The three loyalist Legions were almost annihilated.

Jericho III
Located in the Spartus Sector of the Segmentum Tempestus. In 694.M39 Dark Eldar pirates attacked the world, destroying its capital city and killing 3,200 Planetary Defence Force (PDF) personnel, another 1,400 civilians, capturing 1,500 PDF personal and 16,800 civilians to use as slaves.

Kaurava (Star System)
The Kaurava System is the star system in the Eastern Fringes of the Milky Way Galaxy in the Ultima Segmentum where, because of the sudden appearance of a Warp Storm, nine separate armies from each of the Milky Way galaxy's most powerful intelligent species clashed with each other in the PC game 'Dawn of War - Soulstorm'. There were four worlds within the system, all named Kaurava, and all of which were capable of sustaining life, making Kaurava a valuable strategic location.

Kronus
Kronus is the Civilised World over which war is waged in the PC game Warhammer 40,000: Dawn of War - Dark Crusade. At the time of the Dark Crusade, Kronus was a former Imperial world that had been under the rule of the expanding Tau Empire for approximately 200 years. Seven of the most potent military powers in the galaxy clashed over the world, including the Eldar of Craftworld Ulthwé, the Imperial Guard's 1st Kronus Liberators, the Space Marines of the Blood Ravens Chapter, the Orks of Warlord Gorgutz 'Ead 'Unter, the Tau Empire, the Word Bearers Traitor Legion of Chaos and a recently awakened force of Necrons. Each army refused to back down, beginning a terrible and unique conflict that would go down into Imperial records as the Dark Crusade. The Blood Raven Space Marines ultimately proved victorious, even following an unexpected conflict with the forces of the Imperial Guard stationed on the world, and returned the planet to the rule of the Imperium of Man. Kronus lies near the Tau Empire somewhere in the Ultima Segmentum, in the Eastern Fringes of the galaxy, boasting diverse conditions and terrain; the population is composed primarily of humans and Tau, with a small number of feral Orks in the fringe regions. The planet's human history runs a fairly long way back, as evidenced by its ancient STC technology, and has been fought over in both the Horus Heresy and the Damocles Gulf Crusade. In addition, Kronus also played host to major fighting during the Horus Heresy, and a few previous Ork WAAAGH! attempts. The planet however, hides a dark secret. It is a Necron Tomb World, which over the span of millions of years, developed its current life-supporting environment. Awoken by an ill-fated human archaeological team working for the planet's Tau rulers, their appearance was made worse by the rapid arrival of several armies on the planet when word got out that the Necrons had awakened on yet another world.

Lorn V
Lorn V is the Ice World that is fought over in the Dawn of War expansion Winter Assault. The planet had already fallen to two separate forces of Orks and Chaos Space Marines of the World Eaters Legion who were servants of Khorne, who were fighting each other for control of the Ice World. In the game, the Imperial Guard's Cadian 412th Regiment was sent to the planet on a mission to salvage an Imperator-class Titan before the xenos and Traitors could find it. A force of Necrons were also buried deep underground, bringing the Eldar of Ulthwé Craftworld to the planet in an attempt to keep them from awakening. In the novel Dawn of War: Ascension, Lorn V is mentioned to have been a former Eldar Exodite world. However, the canonicity of this statement is debatable since other plot elements in the novel conflict with those in the game, for example Farseer Taldeer being from the Biel-Tan Craftworld instead of the Ulthwé Craftworld, and the Blood Ravens assisting the Cadian 412th Imperial Guard Regiment instead of the Ultramarines as seen in the game.

Luther McIntyre IX
Luther McIntyre IX is a particularly infamous deathworld frequently referenced by Games Workshop publications but rarely explored in detail. Multiple sources since 1st edition Warhammer 40,000 vaguely indicate that it is a hot desert deathworld. One of the known lifeforms nature to this this world is the Mica Dragon, whose teeth formed the chainsaw edge of Khârn the Betrayer's axe Gorechild.

Macragge
Macragge is the homeworld of the Ultramarines and the capital world of the Realm of Ultramar at the Eastern Fringe. In 745.M41, Hivefleet Behemoth was destroyed in the Battle of Macragge at the expense of the Ultramarines 1st Company.

The immense strength of the veteran 1st company, led by Captain Invictus, was forced into the fortress of the Ultramarines by the Tyranids. The battle, or 'Last stand of the First Company' took place in the Lower Generatorium of the fortress. The Third Company had made its way to where the last stand occurred. Bodies of Tyranids were piled everywhere, and in the middle of the room, the final remains of the First Company remained right next to their battle brothers, where they had fought back to back in a determined rage.

Mars
Mars is the twin planet of Holy Terra, and one of many long-inhabited worlds near to the Cradle of Humanity. It is the home and power centre of the Adeptus Mechanicus, the ancient  priesthood of the Machine God, and the heart of their galaxy-spanning monopoly on technology. Mars is peppered with towering hive cities, and there is very little of the planet's surface which remains untouched by the constructions of the Techpriests.

It is hinted that C'tan, The Void Dragon, may be dwelling under the surface of Mars. A piece of writing in the Necron codex, in which Abaddon the Despoiler is seen seeking information from a daemon, indicates the location of the C'Tan. The daemon hints that the Void Dragon is at Vaul's Moon. Vaul is the Eldar god of the forge. Since Mars is the greatest forgeworld in the galaxy, it can be assumed the Dragon may be there. There are also other pieces of backstory that provide similar evidence. This point is open to debate though and has not been confirmed by Games Workshop. It is also possible the Adeptus Mechanicus worship the ancient C'tan (although unknowingly) as they worship a figure called the Machine Spirit, which is possibly the Void Dragon, while the Omnissiah, the Machine Spirit made manifest, is the Emperor of Mankind himself. Therefore this leaves much debate in the topic, since in the same book from The Horus Heresy states that the Emperor in a past life defeated the dragon and imprisoned it, while it was recovering on Earth in the country of Libya.

The planet is home to three Titan Legions, one of them the Legio Ignatum. The other two are classified.

Medusa V
Medusa V was an Imperial mining world in the Medusa System of the Ultima Segmentum that was close to a Warp phenomena known as Van Grothe's Rapidity, better known as Hell's Slingshot for the way Imperial ships used it to drastically increase the speed of their transit through the Eastern Fringes of the galaxy. In the last years of the 41st Millennium, the Rapidity vastly increased in size and intensity, and moved to envelop the entire Medusa System. However, even though the fate of the planet was sealed, it became a major battlefield, as every major faction of the Eastern Fringe, from the Imperium and the Forces of Chaos to the Tau, Eldar, Dark Eldar, Tyranids and the Necrons, found a stake in the planet's approaching destruction. The Imperial forces, Guardsmen and Space Marines alike sent to defend the planet, were victorious in their efforts to evacuate the Loyalist civilian population of the world before it fell to the Warp. Sicarius, captain of the Second Company of the Ultramarines Chapter, fought there to stop the plans of the Chaos Sorcerer Ygethmor of the Black Legion to become a Daemon Prince, while a splinter fleet of the Tyranid Hive Fleet Kraken sought to hunt down a special Lictor subspecies and absorb it into the Tyranid swarms. After heroic fighting on the planet, the Warp storm finally overcame it. Yet, by the heroic efforts and costly sacrifices of the Imperial Guard and the Space Marines for the Emperor the planet was saved from eternal damnation at the hands of the Ruinous Powers of Chaos.

Menazoid Epsilon
This world and Menazoid Sigma were part of the theatre known as the Sabbat Worlds Crusade. Guard units from the Tanith First, Vitrian Dragoons, Oudinot Irregulars, Afghali Ravagers, Pragar, Modian, Cadian Armoured, Sarpoy Mechanised Cavalry, Borkellid Hellhounds, Samothrace 4th, 5th and 15th, Ketzok 17th, Lattarii Gundogs and Jantine Patricians converged on a target that turned out to be an intact STC for Iron Men. After an assault where the Jantine Patricians turned on the Tanith First and a series of monoliths trigged a trap that destroyed many guardsmen, Colonel-Commissar Ibram Gaunt destroyed the template as it began to produce chaos tainted Iron Men.

Minea
A Hive World in the Ultima Segmentum. It has a population of 154 billion. There are roughly 2 million Imperial troops gathered there. The closest Space Marine Chapter is Crimson Scions. It has a planetry draft of 1,249,000 per annum. Its chief exports are Banedax Ore and Phosgene Gas

Mordax Prime
A Forge World in the Scarus Sector. Almost completely destroyed during the aftermath of the Horus Heresy when it suffered heavy attack from Traitor forces escaping to the Eye of Terror including a large fleet fleeing from Mars. Known to have been defended successfully with the aid of a force of Iron Hands in M39 against enemies unknown. Suffered increasing attacks from elements of the Night Lords and Black Legion before and during the 13th Crusade culminating in a huge Ork Invasion. It was defended unsuccessfully by a combined Imperial Guard, Skitarii and Black Templar force. Adeptus Mechanicus artifacts were looted by Chaos forces under the cover of the Ork invasion, but they were severely hampered by the Ork forces who inevitably turned on their paymasters. The planet fell to the "Green Kroosade", and was quickly renamed Mordakka Prime by the Orks.

Mordian
Mordian is a Hive World with tidally locked rotation on its axis, leaving one side of the planet locked in eternal night while the other side is cooked by the Mordian sun. Ruled by a totalitarian regime that controls the planet's meager supplies, Mordian is defended by the elite Iron Guard - a highly disciplined army wearing ornate uniforms. Many of their enemies have underestimated these ranks of colorfully-uniformed troops, only to find out that they were tough and uncompromising 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 Nostramo.

Murder (One Forty Twenty)
Murder was a death world discovered during the Great Crusade by the 140th Expedition under the command of the Blood Angels Space Marines. Shortly after a combat drop, the planet was consumed by warp storms, which effectively prevented reinforcements from landing. As a result, the Blood Angels were dropped into the planet and wiped out to a man by the lethal Megarchanid forces. The Emperor's Children were similarly destroyed when they attempted to relieve the Blood Angels. Eventually, the Luna Wolves under the command of the Warmaster Horus, were able to successfully counterattack with the aid of Sanguinius. The planet was then destroyed by Exterminatus.

Necromunda
A Hive world in the Imperium of Man's Segmentum Solar, Necromunda is a major producer of munitions for the Imperial Guard. Necromunda's great forges produce lasguns, autoguns, shotguns and boltguns, among other weapons. The planet also levies huge numbers of troops for the Imperial Guard (most notably the Necromundan Spiders), as well as other supplies. Necromunda is typical of most large Imperial hive worlds, in that the lower portions of its hive cites are rife with powerful gangs. The world is the setting for the Necromunda tabletop skirmish war game.

Nostramo
Nostramo was the former homeworld of the Night Lords Chaos Space Marines Legion. The hive world of Nostramo was shielded from its sun by an enormous moon as well as tremendous pollution. As a result, the planet was covered in almost perpetual darkness. Nostramo boasted five major cities, Nostramo Prime through Nostramo Quintus, from which the planet’s vast reserves of naturally occurring adamantium were processed and exported off-world. Nostraman society was dominated by a ruling oligarchy and its criminal thugs, and any who protested the status quo were trampled down or killed. Depression was widespread and overpopulation was prevented not through war, disease or legislation, but the suicide of despairing Nostramans. The Nostramans were superficially similar to normal humans, save for their lack of irises (the pupil having expanded for better night vision), and albinism, though recessive, was common. Then the Primarch Konrad Curze arrived after being kidnapped through the Warp from Terra by the Ruinous Powers of Chaos. The impact of the infant Primarch's gestation capsule upon Nostramo left a massive tunnel boring almost through to the planet’s core. Curze later adopted the name Night Haunter and decimated the hierarchy’s ranks until he was the sole ruler of the planet. Social equality was enforced through Curze’s horrific acts of retribution, until the Emperor arrived and Curze joined the Space Marine Legion that had been created from his genetic material. The arrival of Imperial rule had removed the last shield protecting Nostramo: ignorance. Aware of the existence of other worlds and light, and that these were ultimately unreachable, Nostramo descended back into chaos. After learning of his world's anarchy, Night Haunter arrived with his fleet and concentrated its fire upon the shaft left by his arrival decades earlier. The planet's volatile core did not hold out for long - the world's unstable tectonics resulted in a massive explosion that wiped Nostramo and its unhappy people from existence.

Ophelia VII
Imperial Cardinal World and the base for the secondary Adepta Sororitas convent, the Convent Prioris (According to Rick Priestley's Rogue Trader and second edition's Codex Imperialis the Prioris is located on Ophelia, while the Sanctorum is on Terra; Gav Thorpe's Sisters of Battle codex however reverses the locations). It is the base of the Ecclesiarchy's Synod Ministra.

Ornsworld
Ornsworld was one of the very few planets which are known to be home to the small Abhuman race called Ratlings. Ornsworld was attacked during the Gothic War by Abaddon the Despoiler, (as perhaps an attempt by Games Workshop to exterminate the small Abhuman subspecies of humanity which was based on the halflings of Warhammer Fantasy).

Pindarus
Pindarus is the home of the Fortress Monastery of the Emperor's Shadows Chapter of Space Marines. Pindarus is a moon that orbits a gas giant called Kagoshima Nineteen, in the Ultimatum Segmentum. It is a Death world and any human settlers are savage and feral-like.

Planet of the Sorcerers
The Planet of the Sorcerers is the current homeworld of the Thousand Sons Chaos Space Marine Legion. The Planet of the Sorcerers is a daemon world located deep in the Eye of Terror. With the fall of his original homeworld of Prospero, Magnus the Red used his sorcerous powers to transfer his City of Light, Tizca, through the Warp to a new planet. This planet is now a daemon world of Tzeentch ruled by Magnus as a Daemon Prince; it is dark, rocky, highly volcanic suffers from constant climatic turmoil and change.

Praetoria
Praetoria is a heavily populated Hive World that lies in a system close to the Imperial naval base at Bakka in the Segmentum Tempestus. The overpopulated Hive-Cities of Praetoria are renowned for their squalor and degradation, and produce some of the toughest gangsters on any of the hive worlds in the Imperium. This vast population works as little more than slave-labour in the huge factory complexes of Praetoria, producing the goods that have made the planet (and its rulers) one of the richest in the Imperium, with a huge fleet of merchant craft that trade all over the Segmentum and beyond. Imperial Guard regiments raised on Praetoria, the Praetorian Guard, are renowned for their iron discipline and bravery, even in the face of the most overwhelming odds. Much of the Praetorians' fame comes from their infamous last stands and subsequent massacres, rather than more glorious victories. The planetary lords of Praetoria hold it is only through fearsome training and draconian punishments for the most minor infringements that the hive-toughened inhabitants of their planet can be made to follow orders and do as they are told in a military unit. Whatever one's views on the training methods used, they seem to work, producing troops that are as ferocious on the attack as they are determined in defence. Games Workshop did, at one time, produce a line of Praetorian Imperial Guard miniatures. They bore a close resemblance to Victorian-era British colonial soldiers who fought in the Zulu Wars of the 1870's.

Prospero
Prospero was the original homeworld of the Thousand Sons Traitor Legion of Chaos Space Marines and their Primarch, Magnus the Red. Chosen by settlers for the planet's isolated position, although far closer to Terra than many colonies, Prospero had few redeeming qualities - no independent resources, little contact with any outsiders and few sources of nourishment. The only reason for setting a colony there was because it was a very good place to hide, and became such for a large community of psychically talented humans. During the Great Crusade Prospero had developed into a paradise world. Many of the vast buildings on the planet were massive gold and marble pyramids. It was a planet with blue skies and gleaming Egyptianesque architecture. One of the many cities was the capital Tizca, the City of Light, where the Thousand Sons held out against the Space Wolves when they were mistakenly declared Traitors to the Imperium through the scheming of Horus. As a result of Magnus the Red's determination to not be used as a pawn of the Chaos Gods, the arrival of the Space Wolves' battle barges went uncontested, their orbit-to-surface ordnance barrages unanswered and their drop-pods unchallenged. Ironically, whilst the attack was underway, the Thousand Sons focus remained on the protection of their sorcerous lore – rushing to save what incalculably precious works they could whilst the righteous, if possibly misplaced retribution of Leman Russ' Chapter went unchallenged. Indeed had a defence of Prospero been attempted, more time might have been bought to evacuate the great libraries of their work. During the fight, Leman Russ finally brought Magnus the Red to combat. Leman Russ swiftly beat Magnus and broke his back over his knee. Laying on the ground unable to move, Magnus stared up at the burning towers of his beloved cityof Tizca. It is that Magnus knew that if he gave his soul to Tzeentch much could be salvaged. Even then he hesitated to damn himself but finally gave in. In this way all of the City of Light's pyramids, towers and libraries were saved and transported to the Planet of the Sorcerers. The planet eventually became a blasted ruin, picked clean by millennia of looters and rogue traders, declared 'exterminatus' by the Inquisition.

Reth
Reth is a pleasure world in the Calixis Sector of the Segmentum Obscurus.

Rogar III
Rogar III is a deathworld featured in the novel Deathworld by Steve Lyons. It resembles the other well-known deathworld Catachan greatly as it is a world almost entirely covered in dense jungle and also because the vegetation of the world grows back extremely rapidly, no matter what happens to it. A unit of Catachan Jungle Fighters landed on the world and discovered that the planet evolves with lightning quickness to all invaders. What would take the biospheres of other planets thousands of years to evolve, takes Rogar III's biosphere only a few days to produce. The planet becomes more dangerous as the violence of the fighting on its surface escalates, similar to an allergic reaction in the immune system of a biological organism.

Sabbat Worlds
The Sabbat Worlds is the name given to a group of star systems along the rimward edge of the Imperium's Segmentum Pacificus and is also the name of the Sector in which those systems reside. Made up of over 100 known star systems, the region is subdivided into several discrete territories, most notably the Newfound Trailing, the Khan Group, the Cabal Systems, the Carcaradon Cluster, and the Erinyes Group. Since 741.M41 a massive Imperial Crusade has been on-going in the Sabbat Worlds to retake the Sector from the control of the forces of Chaos.

Sarosh
Sarosh was a temperate planet which was the site of resistance to the Imperium's rescue attempts in the early parts of the Great Crusade. Here elements of the Dark Angels fought a creature of the Warp. The creature had been summoned by the fanatical Chaos-worshipping local populace through the murder of millions of people.

Stalinvast
Stalinvast was a hive world covered in coral-like city growths used in the manufacturing of weapons for the Imperium, between which grew vast blue-green jungles filled with teeming life and vicious predators. Stalinvast was subject to a genestealer infestation which was cleared out, at a vast expense of lives, by a purge led by Inquisitor Harq Obispal. He was given free rein in this by the planetary governor Lord Voronov-Vaux, who was suffering from a minor hereditary mutation, thus being in no position to argue with a member of the Inquisition. Stalinvast was soon after rendered lifeless by an exterminatus order given by Inquisitor Jaq Draco, executed by a life-eater virus bombing. It was subsequently re-classified as a Dead World.

Tallarn
Tallarn was described in Tallarn Desert Raiders, by Rick Priestley, White Dwarf 185. It is a harsh desert planet in Segmentum Tempestus, and the home of the Imperial Guard's "Tallarn Desert Raiders" regiments.

When it was first discovered by Imperial settlers in the 29th Millennium it was classified as a verdant agri-world. However, around the time of the Horus Heresy, the rebel Iron Warriors legion--intending to destroy all potential resistance before landing--virus-bombed the planet from space, rendering it an inhospitable desert. Only then did the Chaos Space Marines land. Tallarn's few survivors emerged from their underground bunkers to stop the Iron Warriors' invasion.

Soon, reinforcements from both sides arrived. It became clear to the Imperial forces the futility of fighting over a destroyed planet but by then there was no turning back. Although it could not be guessed at the time, the Chaos legion were motivated beyond mere destruction. Since the poisoned environment made it impossible for infantry to operate outside of protective shelter, the only available option of battle was that of armored tank warfare. The largest tank battle in human history erupted on the surface of Tallarn. By the end of it, the Iron Warriors were defeated, and the wreckage of over a million tanks littered the sands.

Approximately twenty years after this, the official Tallarn Desert Raiders military force was formed. These regiments specialised in desert fighting, and were highly adept at ambushing enemy forces in the desert.

The Tallarn Desert Raiders continued their attack on various worlds which had turned to Chaos until sometime around the 30th Millennium, when they were recalled. The "Cursus", a Chaos relic of black stone which had led the Iron Warriors to the world was discovered deep under the desert sands. Immediately after finding this relic both Eldar of the Biel-Tan craftworld and Iron Warriors spilled from the sky once more, to attempt to claim this relic. After months of fighting, the Eldar and Tallarn Desert Raiders formed an alliance and destroyed the Chaos forces.

After their combined victory over the Chaos hordes, both races exchanged their promises of friendship, before the Eldar departed in peace. The Tallarn re-entombed the Chaos relic beneath the sulphur sands and turned their backs on it.

Taros/T'ros
The present Tau mining world of T'ros was originally an Imperial mining world called Taros. It became a Tau Third Expansion Sphere Colony following the Tau Empire's exploitation of the Imperium of Man's distraction with the onset 13th Black Crusade when large numbers of Imperial forces were diverted from the Eastern Fringes of the Segmentum Ultima to the defence of Cadia and the Imperial space surrounding the Eye of Terror from the Forces of Chaos. The Tau annexed the planet and successfully defended it from an Imperial counterattack led by an army of the Imperial Guard. The capital city of the arid planet is the city of Tarokeen. T'ros is today mainly inhabited by Gue'vesa (humans loyal to the Tau Empire) who were formerly citizens of the Imperium but became turncoats because the Tau seemed to offer a better life.

Tartarus
Tartarus was the planet fought over between several different factions during the plot of the PC game Warhammer 40,000: Dawn of War. It was classified as an Imperial Civilized World that had frequent problems with raids by Orks. During a terrible Ork invasion, the Blood Ravens's 3rd Company, led by Brother-Captain Gabriel Angelos, were called in to assist. But the situation turned out to be more than just a simple Ork incursion. Long before, the Eldar battled a powerful Greater Daemon of Khorne on the planet and finally, at terrible cost, managed to seal it inside a stone known as the Maledictum. Chaos Space Marines of the Alpha Legion had also come to the planet, seeking to gain power by releasing the Daemon of Khorne; the Ork WAAAGH! had in fact been instigated by the Traitors, for the purpose of distracting the Imperial forces from their true objective. The Blood Ravens battled the Orks, Eldar from the Craftworld of Biel-Tan, and the Alpha Legion, and were victorious, but ultimately failed to prevent the release of the Greater Daemon because of a terrible mistake made by Captain Gabriel Angelos who was the Blood Ravens' Force Commander on the world. The Blood Ravens evacuated the planet as a Warp Storm called by the Greater Daemon engulfed it, while Angelos swore to track down and destroy the daemon. It is highly likely that the planet is close to the Eye of Terror in Segmentum Obscuras, as Angelos noted: "Tartarus has endured several Black Crusades led by the terrible Chaos Champions."

T'au
See the History section under Tau (Warhammer 40,000) for more details.

T'au is the homeworld of an alien race known as the Tau. It was discovered and categorised by the Adeptus Mechanicus' Explorator vessel Land's Vision a few thousand years before the emergence of the Tau as a space-faring race. Before the Imperium could cleanse the planet of the then-primitive Tau population, a freak warp storm occurred and effectively sealed the planet and the surrounding region off. In the few thousand years since, the Tau underwent very rapid technological evolution, emerging as a technologically advanced race as the warp storm dissipated.

T'au is described in the Last Chancer novel "Kill Team" as being warm and desertlike. Preference for planets like T'au drives Tau colonization towards certain planets and away from others.

Terra
Terra (also called Holy Terra or Earth) is the future incarnation of our Earth.

Throne world of the Imperium, Terra is the homeworld of the Emperor and of the human race. Before the Great Crusade, Terra was plagued by a long age of war and anarchy known as the Age of Strife. Terra is perhaps the most massive Hive World within the Imperium, with a population of countless trillions. The bulk of Terra's population is divided into the Adepts (servants of the Emperor and his Imperium, including officials, scribes and workers) and non-Adepts (the far less privileged common citizens.)

Terra's entire surface, with the exception of the Antarctic region, is covered in labyrinthine edifices of state, including the Imperial Palace, the Ecclesiarchal Palace and many departments of the Imperial government. The base of the Inquisition on Terra is beneath the ice caps of the south polar region.

Billions of pilgrims flock to the planet every day, eager for a glimpse of the Imperial Palace or one of the untold number of gargantuan Imperial Cathedrals. Such is the scale of the Imperium that many of these pilgrims' journeys were started by their ancestors and only generations later will a member of the family complete the pilgrimage. Many will set out hopeful and never come close to their goal. Terra is the resting place of the Immortal Emperor of Mankind, where he has sat in - stasis - on the life-preserving Golden Throne, neither alive nor dead, for over ten thousand years. He and the Palace are guarded by the Adeptus Custodes. Among them is a select inner corps of three hundred who never leave his side, known as the Companions.

Within the Imperial Palace complex is the Chamber of the Astronomican. The Astronomican is the psychic manifestation of the Emperor's will - a beacon, beamed from Terra and powered by a "choir" of ten thousand specially-trained psykers, that provides a reliable reference point which Navigators can utilize within warp space. These psykers are chosen from among those brought from other parts of the Imperium to Terra aboard the Inquisition's Black Ships. Other psykers, if considered powerful enough, are recruited into the Adeptus Astra Telepathica, the department forming the network of interstellar communication for the Imperium.

Luna, (Terra's moon) has also been colonized and is home to immense planetary defense lasers charged with protecting Terra from invasion. These defenses inflicted savage losses on the invading rebel fleets of Warmaster Horus, during the latter stages of the Horus Heresy. Luna also gives its name to a class of Imperial Cruiser called the Lunar Class.

Thracian Primaris
For a time the capital of the Helican subsector in Segmentum Obscurus, Thracian Primaris is a hive world. Its decline followed an atrocity orchestrated by renegade Inquisitor Quixos in 337.M41 and its position of dominance was overtaken by Eustis Majoris.

Titan (moon of Saturn)
Titan, the largest moon of Saturn, is the legendary homeworld of the elite Grey Knights Space Marine Chapter, the Chamber Militant of the Ordo Malleus of the Inquisition. A huge basalt fortress punches through the barren landscape of this harsh world, it is here newly selected recruits are brought, for an extensive program of combat training, memory-wiping and faith screening, before initiation into the famed Chapter's attack forces.

Typhon Primaris
Typhon Primaris is a jungle world found in the Aurelia sector, revealed in the video game Dawn of War II. It's population primarily consists of Imperial citizens and Feral Orks. During the events of Dawn of War II an Eldar Warp Spider Exarch was provoking the Orks to attack Imperial outposts and villages, and the Space Marines intervened. However, unknown to them was that the planet had a Genestealer infestation and some plants and animals became mutated, killing livestock. Soon after, a Tyranid Hive Fleet appeared over the planet, threatening to engulf the entire system.

Tsagualsa
Tsagualsa is a planet on the Eastern Fringe, notable for being the base of the Night Lord's Primarch Night Haunter and his operations in the Horus Heresy and also the location of his death at the hands of the Callidus assassin M'Shen.

Ullanor
During the Great Crusade Ullanor was overrun by Orks, in the largest Ork Waaagh!! ever encountered in Imperial history. Supported by the White Scars and Ultramarines, The Emperor, Horus an entire continent in a matter of weeks to create a parade ground sufficiently large to stage a Triumph for the massed Imperial forces. It was at this triumph, attended by nine Primarchs, that the Emperor promoted Horus to the rank of Warmaster and announced his intention to return to Earth. So ending the brunt of the Great Crusade.

Valhalla
Gaining its name from the Viking warrior-heaven, Valhalla, like Tallarn, was once a verdant and beautiful world. Also like Tallarn it suffered a destructive catastrophe: sometime after its discovery by the Imperium, it was hit by a comet. The catastrophic effects of the impact sent the planet into an ice age which, ten thousand years later, is still in place, with temperatures that freeze blood solid and winds that can shear flesh from bones. Valhallan Imperial Guard units are adept at surviving in these conditions.

Valhalla was assaulted by an Ork Waaagh sometime in the 32nd millennium, where the greenskin horde very nearly took over the planetary food supply; if that had fallen, Valhalla would be doomed. But the tenacity of the defenders destroyed the Waaagh! and saved themselves from annihilation.

Vivaporius
A bridgehead planet that was under threat by the Tyranids, but eventually saved. The plantlife and terrain features in some areas were so large that they posed maneuvering and orientation problems to even the Titans. The Tyranids were not there to strip the planet bare of resources as they usually did, but rather to seize control of lured Eldar and Imperial Titans, having found a way to forcibly overtake the mental links. All in all, Imperial casualties included at least three million Guardsmen, two squads of Ultramarines, and two Titan crews. The Tyranids eventually fled into deep space after their presence in the mental links was forcibly killed off.

Vraks
A world known as the stage of a rebellion starting in 812.M41 by a rogue Cardinal. His forces consisted of the local PDF supported by the Alpha Legion, World Eaters and Death Guard Leigons, as well as a number of militia troops under his complete control. A siege was enacted by the Imperium by the regiments of the Death Korps of Krieg and members of the Dark Angels chapter. The war is characterised by the many trenchworks thrown up by the Imperiums as is customary when the Death Korps are present. The war is detailed in Imperial Armour books 5 and 6.

Xerxes Quintus
Xerxes Quintus is the fifth planet of a harsh white sun. It had lost contact with the Imperium thousands of years before and had no knowledge of the origins of human settlement there or of the Emperor of Mankind. It was an agricultural world harbouring a large percentage of mutants and psykers. This generated a tradition of neighbours raising each other's children so that their parents would not have to condemn their own offspring if they proved to be tainted. The language is a highly bastardized version of High Gothic punctuated by oaths. Of religious beliefs they are heretical, holding no saviour figure but rather a reviling of the God of Change, which is how they saw the actions of Chaos in causing mutation.

It is most notable as the birthplace of Inquisitor Jaq Draco, whose parents were adepts of genetics given a life assignment to helping reabsorb Xerxes Quintus into the Imperium. The planet had been recontacted by the Imperium approximately a century before Jaq's birth and plans were being made to utilise it as an agricultural export world, which would in turn allow exploitation of the mineral wealth of its sister world Quartus.

Yu'Kanesh
Yu'Kanesh  is a Tau desert planet being attacked by the Imperium's forces in the beginning of the PC game Warhammer 40,000: Fire Warrior.