- "Beautiful on the surface, but rotten underneath. Don't ever, even for a second, doubt that this is the most dangerous world in the galaxy.... Danger does not always come in the shape of Orks with bolters, Ragnar. This world is where the elite of the Imperium have gathered. We are talking now of the most ruthless, ambitious, unscrupulous collection of rogues ever culled from a million planets. This is the place they have come to realise their ambitions, and on Terra they can, and will not let anything stand in their way. Not me, not you, not their own kin if need be."
Terra, or, in the most ancient records, "Earth," is the Throneworld of the Imperium of Man and the original homeworld of Mankind and of the God-Emperor. It is the most sacred and revered place in all the million worlds that comprise the Imperium. Billions of human pilgrims from across the galaxy flock to Terra -- even the barren and contaminated soil that these pious folk now tread upon when they reach humanity's homeworld is considered sacred by the faithful of the Imperial Creed.
Terra is effectively a globe-straddling temple dedicated to the worship of the Emperor of Mankind. The planet is home to the primary headquarters of many important Adepta of the Imperium since it serves as the capital world of the Emperor's realm. There is a great fear of Space Marines amongst the people who dwell there, due to events dating back to the Horus Heresy, when much of the planet was levelled and terrorised by the actions of the Traitor Legions.
Before the Great Crusade, Terra was plagued by a long age of post-apocalyptic civil war and anarchy known as the Age of Strife, which only came to an end when the Emperor personally waged the Unification Wars to reunite all the Terran factions under His own enlightened leadership.
Today Terra is the slow-beating heart of the Imperium, a sacred world of power and majesty that has become legend for most of the people of the galaxy. It is the site of the Golden Throne; the demesne of the divine Emperor of Mankind. The breathtaking architecture of its soaring buildings strike awe into the hearts of the millions of supplicants below.
Forbidding statues of angels and Primarchs loom down from their eyries, their sightless stare driving out all thoughts of heresy. It is considered such a blessing to set foot upon Holy Terra that most of the pilgrims who manage to reach its polluted surface never leave.
Terra is perhaps the most massive Hive World within the Imperium, with an uncounted population that numbers several hundred billion human beings. The bulk of Terra's massive population is divided between the upper class that includes the Imperial nobility and Adepts of the Adeptus Terra and the masses of the lower classes who serve as basic labourers.
The upper class is comprised of the official servants of the Emperor and His Imperium, including Imperial officials, Ecclesiarchy clergy, the aristocratic families of the Navis Nobilite, military officers, scribes, and bureaucrats.
The teeming masses who comprise the Terran lower classes are far less-privileged, and many of them are nothing more than serfs or thralls who toil in the Throneworld's countless manufactoria, providing the infrastructure that keeps the heart of the Imperium's byzantine bureaucracy functioning. Terra has one moon, Luna, which is an inhabited and highly populous Civilised World of the Imperium in its own right.
The Age of Terra, also called the Age of Progress, is the name given by Imperial scholars to the time from the dawn of Mankind's civilisation before the Imperial Calendar was instituted in the 1st Millennium AD to the founding of the first truly united interstellar human civilisation at some point in the 15th Millennium. Cities such as Atlantys and Nova Yourk are cited as being the most legendary and ancient cities of Old Earth in this time.
Nations now known in the oldest and most incomplete fragments of Imperial records only as Jermani, Merica, Britania, and Bania are said to have prospered, competed and wilted during this legendary time when humanity was slowly taking its first steps out towards the stars.
For the next 10,000 standard years, during the era called the Dark Age of Technology in Imperial chronologies, Terra served as the capital of Mankind's first galactic civilisation. This period was a Golden Age of scientific advancement when many technological wonders such as the Standard Template Construct (STC) databases and the artificially intelligent Men of Iron were brought into being.
Humanity developed the Warp-Drive and spread at an explosive pace across the galaxy, settling thousands of new colony worlds and making first contact with the other intelligent races of the galaxy, including the Aeldari and the Orks. This period ended in violence and horror as the Men of Iron revolted against their human masters and the first widespread appearance of human psykers caused the deaths of hundreds of millions of people when these men and women, unprepared to wield their new powers, unleashed the horrors of the Warp upon their unsuspecting fellow citizens.
The final nail in the coffin for the advanced human civilisation of this period came when the gestation of the Chaos God Slaanesh in the Immaterium led to the onset of giant Warp Storms across the galaxy, completely disrupting interstellar travel and communications. Many human worlds, now isolated from one another, regressed to a pre-industrial state, the glories of their past lost to myth, legend and small stockpiles of archeotech.
Terra itself was consumed by terrible civil wars between nations of techno-barbarians that began in the 27th Millennium and resulted in the use of biological, chemical and thermonuclear weapons of mass destruction that killed billions and forever scarred the sacred landscape of Mankind's homeworld.
Only with the end of the Age of Strife in the 30th Millennium following the birth of Slaanesh and the Fall of the Eldar was sanity restored to the people of Terra when the Emperor of Mankind first rose from deliberate obscurity to launch the Unification Wars that would unite all the nations of Terra beneath His rule and formally establish the Imperium of Man.
After forging an alliance with the Cult Mechanicus of Mars to allow the Tech-priests to maintain their autonomy and religious freedom in return for providing the newborn Imperium with the starships, materiel and war machines it would need to reunite humanity under the Emperor's rule, the Master of Mankind unleashed the Great Crusade upon the galaxy.
As the Imperial Expeditionary Fleets loaded with Space Marines, Imperial Army troops and Mechanicus Titans once more brought Mankind under a single rule defined by the secular Imperial Truth in the early 31st Millennium, the current Age of the Imperium finally dawned.
The Emperor's dream of a new Golden Age of reason and progress for Mankind collapsed in the wake of the galaxy-wide Imperial civil war known as the Horus Heresy. The Warmaster Horus, Primarch of the Sons of Horus Legion and leader of the Great Crusade after the Emperor retired to Terra, was corrupted by the Ruinous Powers of Chaos and rebelled against his father.
Fully half of the Space Marine Legions, the Imperial Army and the ancient Mechanicum threw in their lot with Horus and the other Traitors and for nine standard years they waged a brutal and total war upon the galaxy, leaving countless worlds blazing in thermonuclear fire as they closed in on Terra.
During the Battle of Terra the Traitor Legions laid siege to the Imperial Palace itself and billions of Terrans died in loyal defence of their Emperor. Hundreds of millions of Terran civilians who became trapped behind the lines of the Forces of Chaos after their landings suffered horribly at the hands of the servants of the Dark Gods. So great was their suffering that a morbid fear of Space Marines became a permanent fixture of Terran culture ever afterwards.
But the Emperor and His Loyalist servants ultimately prevailed, and slew Horus at the height of his power on the bridge of his own flagship, the terrible Gloriana-class Battleship, Vengeful Spirit, in high Terran orbit. But the price was high, for the Emperor was mortally wounded and only survived by having His ravaged body interred within the cybernetic life support mechanisms of the arcane device known as the Golden Throne. Though the Emperor's mind remained fully empowered and active within the Immaterium, he could no longer directly communicate His wishes to those who remained behind to govern His Imperium.
And so for the last 10,000 Terran years stagnation, technologically, culturally and even morally, has come to define the Imperium of Man. The Imperial Truth's official atheism has wilted in the face of the terrible dangers that confront Mankind in the Milky Way Galaxy, replaced by the comfort of a religion that holds that the Emperor of Mankind is the God Incarnate of humanity.
Terra has become the heart of an interstellar Imperium stretching across tens of thousands of light years and encompassing more than 1 million inhabited worlds, though it does so through the administration of a galactic government that is at best an uncaring, faceless bureaucracy and at worst a brutal, xenophobic and narrow-minded tyranny. Hundreds of billions of people now call the sacred soil of Terra home, but they are packed into the human warrens known as hive cities, which are islands of tortured civilisation in a vast, toxic urban landscape that stretches across the entire world.
The lucky are able to find work within the bureaucracy of the Imperial Administratum, while the majority are condemned to the poverty and heartbreak of lives as common manufactorum labourers or serfs. In the late 41st Millennium, there is no doubt that Terra will become the scene of Mankind's ultimate salvation at the hands of the Emperor's loyal servants...or the last outpost of humanity to fall before a tide of heretical rebellion, xenos genocide and Chaos damnation.
Age of Terra, M1-M15
Next to nothing is know about Terra's early millennia during the so-called Age of Terra, save that it was between the 1st and 15th Millennia AD that Mankind made their first forays into space, notably colonising Mars. Warp travel was at this point was technologically impossible, meaning most space colonies were self-sufficient and isolated by long, dangerous sub-light speed journeys.
Likewise, not much is known about the Age of Technology and Age of Strife that followed, or why Terra was spared the annihilation that met countless other human-settled worlds. It was at this time that Terra and Mars made ancient agreements that would tie the fates of both planets forever, with Mars at this time a hub of manufacture, scientific research and commerce.
Unification of Terra, Late M29-M30
Towards the end of the Age of Strife -- several thousand standard years during which the first galaxy-spanning empire of Humanity crumbled and fractured into isolated fragments -- the Emperor of Mankind first revealed Himself to Humanity. He began reconquering Terra with an army of Thunder Warriors during the so-called Unification Wars, which were the genetically modified super-soldiers who preceded the Space Marines. The various techno-barbarian empires on Terra were destroyed with this unstoppable army, and the Emperor soon controlled the whole planet -- with designs on taking back the entire galaxy.
The Great Crusade and Horus Heresy, M30-M31
The Great Crusade launched from Terra, which itself became a key battlefield of the Horus Heresy, with the final, climactic conflict seeing the planet invaded en mass by the followers of the Warmaster Horus during the Battle of Terra.
The Beheading, M32
With the Emperor incapacitated during the Horus Heresy, leadership over the Imperium fell to the High Lords of Terra. This did not always go smoothly, such as in the mid-32nd Millennium, when the High Lords were slain by the Grand Master of Assassins, Drakan Vangorich, in an event called "The Beheading" who then ruled the Imperium for solar decades before being deposed by a combined strike force of Space Marines.
The Nova Terra Interregnum, M35-M36
The Imperium was once split in twain by political strife during the so-called Nova Terra Interregnum when the Ur-council of Nova Terra established a second, parallel capital to the Imperium.
The Age of Apostasy, M36
The Nova Terra Interregnum ended, only to be followed by a new schism. Ecclesiarch Goge Vandire struggled for power with the other High Lords of Terra. As tensions escalated, several Chapters of Space Marines assaulted Terra in order to remove the tyrant from office. Vandire was eventually betrayed by the holy military order that would become the Sisters of Battle.
Age of the Dark Imperium, M41-M42
With the opening of the Cicatrix Maledictum following the fall of Cadia in the 13th Black Crusade, the beacon of the Astronomican faltered, and Terra itself was assailed by daemons as Khorne launched a brutal assault on the Imperial Palace known as the Battle of Lion's Gate. A joint force of Primaris Space Marines, Adeptus Custodes and Sisters of Silence repelled the assault, but it stands as a dire warning of just how far the Chaos Gods could reach if the Golden Throne were to fail completely...
Terra in the 41st Millennium is an Imperial Hive World, the largest in the galaxy. The Earth was stripped of all forms of natural resources many millennia ago; its soil is utterly barren and its atmosphere is now a fog of industrial pollution. Massive, labyrinthine edifices of state sprawl across the vast majority of the surface.
What remained of Terra's oceans after the thermonuclear wars that scarred the planet during the Age of Strife boiled away in the years after the Horus Heresy due to the immense heat produced by the hundreds of billions of people who have been compressed into the world's limited living space. All liquid water to meet the Terran population's needs is now delivered from orbit by freighters who take large ice-bearing comets from the outer Sol System and bring them into Terran orbit to be melted down and dispersed to the population.
Many mountain ranges have been leveled -- perhaps all but the Himalazian range (the Himalayas), which remain untouched due to the genetic engineering laboratories said to lie beneath them where the Emperor created the Primarchs and the first Space Marines after the Unification Wars more than ten millennia ago.
The chambers of the Astronomican also course throughout the whole mountain range. Despite being devastated during the Horus Heresy and by the terrible wars fought across the surface of the world by the nations of techno-barbarians during the long Age of Strife, Terra is still the most vastly-populated and built-up hive world in the Imperium. Beneath countless layers and millennia of urban accretion, catacombs hold older cultures radically different from the surface ones.
Much of the population of Terra exists in the most terrible squalor, their greatest hope that one of their offspring might be accepted into the Adeptus Terra, the Priesthood of Earth and bureaucracy of the Imperium, as a Menial, an Adept of the lowliest sort.
A square metre of land on Terra costs more than a palace on any other Hive World; only the most wealthy citizens can afford to own a small section of land. 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 of the Adeptus Ministorum and the many departmental headquarters of the Adeptus Terra, the Imperial government.
The headquarters of the Imperial Inquisition on Terra lies beneath the ice caps of the southern polar region of Antarctica and is one of the most secure installations in the entire Imperium.
Terra was also originally home to the massive concentrations of industry known as "Orbital Plates," which in earlier times were referred to as "space elevators." By the time of the Great Crusade in the 30th Millennium most made use of anti-gravitic technology and no longer had any need to be anchored to the planet's surface.
These orbiting cities were old even in the time of the Unification Wars, but during the Horus Heresy, in the years before the start of the Battle of Terra, the Primarch Rogal Dorn, who had been named Praetorian of Terra by the Emperor and was thus in charge of its defence from Horus' invasion, had them all dismantled, moved, or abandoned over questions concerning their safety and loyalty.
In the 41st Millennium there are still countless orbital defence platforms circling Terra, and the Throneworld is the most heavily fortified and protected planet in the galaxy.
Oceans of Terra
By the time of the Unification Wars in the early 30th Millennium, there was only one remaining ocean on Terra -- the so-called "Great Ocean" -- which was actually the remains of the ancient Pacific Ocean. The size of the Pacific was vastly smaller than in prior eras, due to the vaporisation of a massive stretch of the ocean during the nuclear wars that had consumed much of Old Earth in the lost years of the Age of Strife.
This missing portion of the Pacific stretched from the Marianas Trench down past Australia and all the way to the frozen continent of Antarctica. The Atlantic Ocean had also been largely vaporised as the great body of water that had once been near Europe was now mostly gone, particularly to the south of what had been the Iberian Peninsula.
Other, smaller, bodies of water may still have remained during this time, as a great sea is recorded to have been present in the region of Eurasia where the Caspian Sea had lain in ages past. These bodies of water still existed at the start of the Horus Heresy in the early 31st Millennium, but by the time of the 41st Millennium, Terra had no free-standing bodies of water, having become a true ecumenopolis, a world completely covered by the dense urban areas of massive hive cities.
The Emperor had sought to create artificial bodies of water to replace what had been lost in the wake of the Unification Wars, but by the 41st Millennium, no liquid water was visible on Terra's surface. Within these human hives toiled the tens of billions of Adeptus Terra bureaucrats and serfs required to keep the decaying heart of the Imperium of Man pumping.
Terra is the heart and Throneworld of the Imperium of Man, and serves as the headquarters for many of its most important Adepta and other organisations. Most importantly, it is the homeworld and resting place of the Emperor of Mankind. The most important places on Terra and the headquarters of the vital Imperial organisations based on Terra include the following:
- Imperial Palace - One of the largest structures on Terra, the Imperial Palace is more like a sprawling hive city than a single edifice. It covers the better part of the Northern Hemisphere, and is guarded by the Adeptus Custodes, the superhuman praetorians of the Emperor who rarely leave the confines of the Palace. It is the heart of the Administratum as well as the home of the Sanctum Imperialis, the great throne room of the Emperor and the location of the Golden Throne. The Palace is divided between the Inner and Outer Palace. It is described as "an endless, black hive of forbidden technology and subterranean passages delving deep within the bowels of the planet."
- Eternity Gate - The largest entryway into the Inner Imperial Palace's Sanctum Imperialis. A mile-long passage leads to the Eternity Gate, lined with the banners of thousands of the greatest and long-dead Imperial heroes, including Lord Commander Solar Macharius. It constitutes the end of the galactic pilgrimage trail or the devotees of the Imperial Cult, and is itself the most important pilgrimage site in the entire Imperium, for almost no one is ever allowed entrance through the Eternity Gate into the Sanctum Imperialis.
- Sanctum Imperialis - The Sanctum Imperialis is the throne room and heart of the Imperial Palace. It is the massive chamber housing the Golden Throne and the Emperor's physical body. It is guarded by a select group of three hundred Adeptus Custodes, the Companions, who are the elite among the elite.
- Central Offices of the Departmento Munitorum - These offices mark the central location of the Departmento Munitorum, a department or sub-division of the Adeptus Administratum devoted to the general administration, personnel assignment, supply and logistics of the Astra Militarum.
- House of Weapons - The House of Weapons is the ancient, formidable armoury of the Imperial Palace. The Adeptus Custodes and the Imperial Fists Chapter are known to store their arms and armour here.
- Tower of Hegemon - This tower is where the Custodes keep their office of watch. Within the tower lies the Watchroom -- the nerve-center for security operations for the Adeptus Custodes and the entire Imperial Palace complex.
- City of Sight - The City of Sight was built within a section of the Emperor's own Imperial Palace in the Himalazian (Himalayan) Mountains. This was the main headquarters of the Adeptus Astra Telepathica during the Great Crusade and the opening days of the Horus Heresy.
- Obsidian Keep - The Obsidian Keep is the current headquarters of the Adeptus Astra Telepathica in the 41st Millennium. Located in the vast Astra Telepathica palace complex on Terra, some psykers captured by the League of Blackships are brought here for training as Astropaths or Sanctioned Psykers.
- Bhab Bastion - The Bhab Bastion was an ancient place of counsel and refuge for warlords and tyrants since before the Age of Strife. Following the Unification Wars, this ancient structure was absorbed into the growing complex of the Imperial Palace. During the Horus Heresy, the Bhab Bastion, alongside the Phalanx, the massive capital ship of the Imperial Fists Chapter, acted as the command centre of the Primarch Rogal Dorn while he oversaw the construction of the defences for the Sol System as the Warmaster Horus' Traitor Legions closed on the Throneworld.
- Tower of Heroes - The Tower of Heroes houses the Bell of Lost Souls, a colossal iron bell that is as massive as a building and adorned with dark runes. The Bell of Lost Souls tolls only when the greatest of the Imperium of Man's heroes perish and can be heard by millions of people across the face of Terra. It rarely rings, but when it does, all resident Imperial Palace servants must be evacuated and sealed within reinforced shelters to prevents the annihilation of their eardrums and subsequent death through lung rupture and embolism. Among its many legends is the holiest of all; that when the bell rings, the Emperor hears the sound even in His long slumber upon the Golden Throne, and sheds a single tear.
- The Shrouds - The Shrouds is the name given to the secret chamber located deep within the confines of the Inner Palace that served as the headquarters of the Officio Assassinorum. It was the primary meeting place of the various masters of all six Assassin Clades and was overseen by the Grand Master of Assassins. During the Great Crusade and Horus Heresy eras, this post was held by Malcador the Sigillite.
- Column of Glory - The Column of Glory is a massive crystalline pillar of multi-hued metals rising half a kilometre high, under a vaulted dome so lofty that clouds form to obscure its frescoed arcs. Studding the Column is hundreds of shattered suits of Power Armour belonging to Blood Angels, White Scars, and Imperial Fists Space Marines, who died defending the Imperial Palace 10,000 standard years ago during the Battle of Terra.
- The Pillar of Bone - The Pillar of Bone is believed to be a monument raised on Terra to the Imperial Fists' courage in an unnamed campaign. In reality it is actually a sacred relic to those privy to the truth about the Chapter within the Imperial Fists. The Pillar is the last remnant of the once-great Imperial Fists fortress-monastery that stood on Terra. It was destroyed during the Horus Heresy in the midst of the Battle of Terra.
- The Investiary - The Investiary was a massive amphitheatre open to the night sky, its broad space once containing the statues of the twenty Primarchs on ouslite plinths in a silent ring. The effigies of the traitorous Primarchs who betrayed the Emperor during the Horus Heresy were once temporarily shrouded. Following the end of the Horus Heresy, the effigies of the Traitor Primarchs were removed entirely.
- The Senatorum Imperialis of the High Lords of Terra - This immense building within the Imperial Palace complex houses the council or Senatorum Imperialis of the twelve highest-ranking political officials in the Imperium, the High Lords of Terra, who rule in the Emperor's name as He no longer can, though His mind is believed to remain active in the Warp, guiding and protecting humanity.
- Great Chamber of the Senatorum Imperialis - This massive meeting chamber is where the Imperial elite hold their "parliament," and is the meeting place of the High Twelve.
- Library Sanctus - The Library Sanctus is an Imperial archive located on Terra. It holds knowledge of some of the oldest and most sinister things in galactic history, such as information on the Men of Iron and the Ymga Monolith.
- Dark Cells - The Dark Cells or "Black Cells" as they are sometimes called, are shadowy oubliettes located deep beneath the Imperial Palace that contain entities and aretfacts that date back to the Age of Strife that could be used to annihilate the Imperium itself if they were to break free or be used by those with nefarious purposes. It is unknown if the Dark Cells are the same location as the Vaults of Rython that were used for an identical purpose by the Legio Custodes before the Horus Heresy. Guarded by the Shield Host of the Adeptus Custodes known as the Shadowkeepers, the technology used to keep them sealed includes runic locks, psychic wards and sanctic circles. The corridors of the Dark Cells are patrolled at all times by a hundred Custodians of the Shadowkeepers. Although neither light, nor sound can escape from the cells, the dread air surrounding the facility is capable of even putting the iron-willed Custodians on edge.
- Adeptus Terra - The Adeptus Terra, known commonly as the Priesthood of Earth, is the actual government of the Imperium of Man, consisting of countless different bureaucratic organisations and the departments within them. Besides the vast, destitute population of non-Adepts that makes up the majority of the planet's populace, much of the rest of Terra's population are members of the Adeptus Terra and of these the largest percentage are Adepts of the Administratum.
- Administratum - The Administratum is the administrative and primary bureaucratic division of the Adeptus Terra. It consists of untold billions of clerks, scribes, bureaucrats and administrative staff constantly working to manage the Imperium at every level, from assembling war fleets to levying taxes and tithes. It is the largest of the departments comprising the Adeptus Terra, and ten billion Administratum Adepts work in the Imperial Palace alone.
- The Forbidden Fortress - The Forbidden Fortress is a vast complex that extends throughout the mountain range of the Himalazians. A single peak is carved to form the Chamber of the Astronomican, where ten thousand psykers continuously power the Astronomican beacon directed by the mind of the Emperor with their own life energies. The "psychic light" of the beacon reaches thousands of light years across the Warp and helps to keep the daemonic entities of the Warp from breaking through the dimensional barrier into realspace. The Astronomican is utilised by the mutant psykers known as Navigators to guide interstellar starships through the otherwise trackless chaos of the Warp. Without it, long-distance Warp travel would be impossible and the Imperium of Man would disintegrate. Access to the Forbidden Fortress is restricted to invitation only. This includes even members of the Inquisition who must still request access.
- Fortress of the Inquisition - The Inquisition's headquarters on Terra is a sprawling and highly secure complex built beneath the south polar ice cap of Antarctica. Located deep underground, this subterranean complex is heavily warded and equipped with psyker dampening devices and null-fields. Only members of the Inquisition and a sparse number of prisoners are permitted to enter this underground complex. The Fortress is overseen by a senior Inquisitor known as "The Castellan," a position which changes annually, to ensure that no man or woman can establish a political powerbase or extend the control of one of the Inquisition's innumerable quarreling factions over this facility.
- Navigator's Quarter - The headquarters of the families of the Navis Nobilite (the Navigators). It is said to be located on a massive island.
- Hall of Judgment - The headquarters of the Adeptus Arbites, the chief law enforcement organisation of the Imperium.
- Officio Assassinorum and the Assassinorum Temple - Although its agents operate throughout the Imperium, this dark organization is based on Terra. Its School of Assassins and most of the temples that comprise the Officio are said to be located on Terra, although their actual locations are closely guarded secrets. The Assassinorum Temple is specifically the headquarters of the Grand Master of Assassins.
- Adeptus Astra Telepathica - The Adeptus Astra Telepathica is the organization responsible for recruiting and training officially-sanctioned psykers for service to the Imperium. The infamous Black Ships of the Adeptus Astra Telepathica travel throughout the Imperium, gathering their tithe of psykers and returning with them to Terra. The psykers are analysed and sorted according to their psychic power and strength of mind in resisting the temptations of Chaos. The novitiates are trained at the Scholastica Psykana for five standard years before being sent for further training elsewhere. Some of these Sanctioned Psykers become Astropaths, specialist psykers who are trained to telepathically send and receive messages over interstellar distances (no other form of instantaneous interstellar communication exists). Others are requisitioned by the Adeptus Astronomica for service in the Astronomican's choir. The most powerful, those who demonstrate a strong enough mental character to resist daemonic possession on their own, often enter the Inquisition for training as Acolytes, with some eventually becoming Inquisitors themselves. Those psykers deemed too weak or dangerous to live become sacrifices to the Emperor; their souls are "fed" into the arcane technology of the Golden Throne so that the Emperor may continue to live and guide the Astronomicon that allows the Imperium to function as an interstellar civilisation. Only psykers that have been trained at the Scholastia Psykana are legally sanctioned by the Imperium; all others are considered illegal, often branded as "witches," and are at risk of being summarily executed as Heretics by the Inquisition's Ordo Hereticus and other organs of official Imperial power.
- The Ecclesiarchal Palace - The headquarters of the Ecclesiarchy, also known as the Adeptus Ministorum, the Ecclesiarchal Palace sprawls over almost the entirety of Terra's southern continent of Australia. It is also home to one of the two major convent-fortresses (the Convent Prioris) of the Adepta Sororitas (the Sisters of Battle) on the Imperium's Throneworld.
- The Cathedral of the Emperor Deified - A massive cathedral of the Imperial Cult that was built near the Ecclesiarchal Palace.
- The Cathedral of the Saviour Emperor - A large cathedral of the Imperial Cult that is quite popular amongst pilgrims. It is said to contain important Imperial relics, including pieces of the Emperor's armour and ashes from the cloak of Roboute Guilliman, the Primarch of the Ultramarines and current Lord Commander of the Imperium. Pilgrims often undertake multi-year journeys to the Cathedral and endure massive lines, only to be granted a mere three solar seconds to be in the presence of these holy relics before they must take their leave and move on.
- Khangba Marwu - Khangba Marwu, also known as "The Vault," was a large underground Imperial prison complex on Terra intended to hold the worst criminals of the Imperium of Man. Its inmates were overseen by the Legio Custodes during the early 31st Millennium. The prison was located in the Himalazian Mountains under the mountain peak of Rakaposhi, and had been constructed at least a thousand standard years before the Horus Heresy began by persons unknown. The prison was home to some of the worst criminals of the Imperium and had been used to imprison several of the tyrants defeated by the Emperor's forces during the Unification Wars.
- Eternal City - The Eternal City is a massive urban area adjacent to the walls of the Imperial Palace in the 41st Millennium that is known to contain both great splendour and horrible squalour, making it a microcosm of Terra itself.
- The Catacombs - The Catacombs are vast underground passages which run beneath Terra, so large that they require oversight by a designated Imperial official known as the Mistress Plenary who is a lesser member of the Senatorum Imperialis, serving at the pleasure of the High Lords.
- Hive Karelia - This ancient city once housed a vast library that contained knowledge of the Dark Age of Technology, but was bombed by Pro-Panpacifists during the Great Crusade era, due to civil unrest and resistance to the Emperor's rule. It had been scheduled for demolition, but Kasper Ansbach Hawser, an Imperial Conservator (historian), managed to succeed in recovering over 7,000 texts from a data archive that had been deemed worthless.
- Hive Tashkent - Hive Tashkent is one of the hive cities of Terra known to exist in the 32nd Millennium at the time of the War of the Beast. It is based on the continent of Asia.
- Himalayic Shelf - Deep beneath this geological construction live the deadly denizens of various rune-locked vaults. The warriors of the Adeptus Custodes often fight in skirmishes intended to prevent them from escaping.
- Manufactora Mericum - Beneath this massive manufactorum complex lie countless tunnels that are used as hiding places for various cults. The warriors of the Adeptus Custodes sometimes enter them to carry out a purge of the cultists when the threat they present begins to grow.
- Walking City - The Walking City was a densely-populated, mobile techno-nomad platform that slowly walked a looping route towards the equator of Terra and back on twenty great legs. During the Horus Heresy, in the days just before the start of the Siege of Terra, the Walking City came under assault by the daemon known as the Lord of Flies, which had used the potent faith of a secret church dedicated to the then-illegal cult of the God-Emperor as a way to manifest in the material realm. The daemon had infected the population, transforming them into plague fly-riddled zombies. The Knights-Errant, led by Nathaniel Garro, were despatched to combat the attack and successfully banished the Chaos infestation.
- White Mountain - The White Mountain was a great subterranean fortress delved beneath a mountain range on Terra. It had been constructed by one of Terra's ancient and unknown warlords and lay in a region that by the time of the Horus Heresy was still irradiated and lifeless from the damage caused to the world by the Age of Strife. The fortress had been taken over by the Imperium and had potent anti-psyker wards put in place so that it could serve as a prison for psykers. The Emperor's intent had been to imprison the potent psychic Primarch Magnus the Red there if he had been successfully extracted from Prospero. Unfortunately, the Space Wolves had attacked that world early in the Heresy against the Emperor's original orders and Magnus had gone over to the service of Chaos, never returning to Terra. The White Mountain was where Malcador the Sigillite ordered a group of Sisters of Silence who had been captured and tortured by the forces of Chaos and then recovered by the Loyalists to be held while his researchers sought to determine what had been done to them. In fact, the altered Sisters were simply part of a plot by the Traitors to assassinate the Sigillite by triggering a subliminal mental command that had been psychically embedded in the mind of Tylos Rubio by the Word Bearers First Chaplain Erebus. Rubio was one of Malcador's Knights-Errant who had fought at the Battle of Calth. The plot was initiated when the White Mountain came under assault by Chaos Cultists and the daemon of Nurgle known as the Lord of Flies. The Knights-Errant were deployed onto the slopes of the fortress to deal with the assault, while Rubio's mental conditioning was triggered by the Sisters of Silence kept within the White Mountain's holding cells. He attacked Malcador while the Sigillite was bereft of his psychic powers due to the fortress' anti-psyker technology. The Sigillite managed to hold off the attack using his hidden Conversion Field and then psychically stripped the mental conditioning from Rubio's mind. On the slopes of the White Mountain, Garro and the Knights-Errant managed to defeat the Chaos assault, though the Knight-Errant and former World Eater Macer Varren was possessed by the Lord of Flies before finding the willpower to force back the daemon's assault and destroy himself using a brace of grenades taken from Garviel Loken. The daemon's hold on realspace was finally destroyed by the Sigillite himself, who used his restored psychic abilities to burn the daemon to ash.
As the Throneworld of the Imperium, Terra is the most heavily defended world in the galaxy. As Terra itself had faced few true threats in the ten thousand years since the end of the Horus Heresy, even the idea of attacking the planet has been seen as ridiculous by many Imperial officials throughout history.
However, the world has always been protected by a multitude of layered defences drawn from every branch of the Imperial military. These include, but are not limited to, the following:
- Battlefleet Solar - The Battlefleet Solar of the Imperial Navy includes not only the largest number of capital ships the Imperium possesses in one fleet, but a vast array of Star Forts of many different types.
- The Phalanx - The mobile fortress-monastery of the Imperial Fists Chapter normally takes up station in high orbit over Terra.
- Astra Militarum - Multiple Imperial Guard regiments garrison Terra, including the Palatine Sentinels, Lucifer Blacks, Katanda Stalwarts, and Terran Praefects.
- Convent Prioris of the Adepta Sororitas
- Adeptus Custodes
- Sisters of Silence - Since the resurrection of Roboute Guilliman and his return to the position of Lord Commander of the Imperium, he has sought to restore the Sisters of Silence to their ancient place of prominence as defenders of the Throneworld.
- Legio Ignatum Titan Legion
- Knights of House Taranis - The Imperial Knights of House Taranis of Mars are always available to lend their aid to the defence of Terra.
- Ordo Sinister
- Adeptus Arbites
- Ordo Custodum of the Inquisition - The Ordo Custodum is a minor Ordo of the Inquisition. Founded in the 35th Millennium, it currently consists of under 50 Inquisitors. They keep a vigilant watch on Terra. The Ordo Hereticus also maintains a large presence on the planet.
- Inquisitorial Storm Troopers
- Officio Assassinorum
- A small detachment of Space Wolves
- Imperial Fists Chapter - The Imperial Fists garrisoned Terra as a full until the War of the Beast in the mid-32nd Millennium when they moved off-world to become a fleet-based Chapter, but elements of the Chapter returned to defend the planet on a semi-permanent basis in the aftermath of the 13th Black Crusade in 999.M41. 
- Crusader Host (30th-31st Millennium) - The Crusader Host was a group of Space Marines drawn from all 18 Space Marine Legions based within the Sol System during the Great Crusade. Their exact purpose is unknown. When news of the Horus Heresy reached Terra, Rogal Dorn had all members of the Host imprisoned in Khangba Marwu, fearing for their loyalty, save for the Imperial Fists members. Some time later, several of these Astartes chose to escape; this small group became known as the Outcast Dead.
- Frateris Templar (32nd-36th Millennia) - The Frateris Templar was the military order of the Adeptus Ministorum until it was disbanded and replaced by the Orders Militant of the Adepta Sororitas in the 36th Millennium after the Age of Apostasy. In the centuries between the 32nd and 36th Millennia when the political power of the Ecclesiarchy was at its height and largely ruled the Imperium, the Frateris Templar provided a significant force to defend the sacred Throneworld from humanity's enemies.
Terra is the resting place of the immortal Emperor of Mankind, where he has sat on the life-preserving cybernetic Golden Throne, neither alive nor truly dead, for ten thousand years. He and the Imperial Palace are guarded by the elite Adeptus Custodes. Among them is a select inner corps of three hundred who never leave his side, known as the Companions.
The Astronomican is a psychic navigational beacon located on Terra, and is a vital navigation aide to the mutant Navigators of the Navis Nobilite who pilot the Imperium's commerical and military starships through the chaotic eddies of the Warp. Without its telepathic guidance, faster-than-light travel through the Warp at distances of more than a few light years at a time would be next to impossible and the Imperium of Man would collapse economically, militarily and politically.
Luna (the 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 Traitor Legion fleets of the Warmaster Horus, during the latter stages of the Horus Heresy.
Luna served as the greatest shipyard and naval base in the Imperium of Man at the time of the Great Crusade and the Horus Heresy. Luna also gives its name to a common class of Imperial Navy cruiser, the Luna-class.
Billions of Imperial Cult 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 of the Ecclesiarchy. In spite of the fact that millions of pilgrims are accepted daily, many more are kept waiting.
Such is the scale of the Imperium of Man in the 41st Millennium, that many of these pilgrims' journeys were started by their ancestors and only centuries later would a member of the family actually complete their long pilgrimage to Terra.
Many will set out hopeful and never come close to their goal. Those who make it are said to never return, crushed to death by their fellow pilgrims, executed by the Adeptus Arbites for straying into restricted areas, or perhaps killed by the crazed and destitute hive city citizens, violent gangers, etc.
The name Terra originates from the ancient Terran language known as Latin which translates as "earth; land"; it is the name of Earth in many modern day Romance languages descended from Latin.
- Codex: Adeptus Astartes - Space Marines (8th Edition), pp. 6-9, 12, 18-22, 25, 28-29, 32, 34, 36-38, 40, 42, 45, 49, 51, 57
- Codex: Adeptus Custodes (8th Edition), pp. 7, 23, 29
- Codex Imperialis (1st Edition), pp. 42, 48
- Codex: Inquisition (6th Edition), pg. 18
- Horus Heresy: Collected Visions (Art Book) by Alan Merett, pp. 352-370
- Gathering Storm - Part III - Rise of the Primarch (7th Edition), pg. 87
- Index Astartes I, "Children of the Emperor - The Emperor's Children Space Marine Legion", "Bitter and Twisted - The Iron Warriors Space Marine Legion", "Lightning Attack - The White Scars Space Marine Chapter"
- Index Astartes II, "Emperor's Fist - The Imperial Fists Space Marine Chapter", "Bringers of Darkness - The Night Lords Space Marine Legion", "Angels of Death - The Blood Angels Space Marine Chapter"
- Index Astartes III, "Chosen of Khorne - The World Eaters Space Marine Legion", "The Lost and the Damned - The Death Guard Space Marine Legion", "Masters of Forbidden Knowledge - The Thousand Sons Space Marine Legion"
- Index Astartes IV, "Sons of Horus - The Black Legion Space Marine Legion", "Dark Apostles - The Word Bearers Space Marine Legion"
- Praetorian of Dorn (Novel) by John French, Part 1, Ch. 3
- Realm of Chaos: Slaves to Darkness (2nd Edition) by Rick Priestley, Bryan Ansell, Mike Brunton and Simon Forrest
- Realm of Chaos: The Lost & The Damned (2nd Edition) by Rick Priestley, Bryan Ansell, Mike Brunton and Simon Forrest
- The Horus Heresy - Book One: Betrayal (Forge World Series) by Alan Bligh, pp. 14-18, 21-25, 27, 29, 32, 40, 44, 49-50, 59, 65-70, 78, 80-81, 83, 85, 88-89, 97, 103-105, 107, 109, 117, 119, 121-122, 126, 128-129
- The Horus Heresy - Book Two: Massacre (Forge World Series) by Alan Bligh, pp. 14-16, 18-19
- Warhammer 40,000: Rulebook (8th Edition), pp. 22-25, 27, 30, 32, 39-45, 48-53, 56, 60, 72, 78, 155
- Warhammer 40,000: Rulebook (6th Edition), pp. 134, 136-138, 146, 148, 152-153, 160, 162, 166-169, 177, 187, 197, 225, 234
- Warhammer 40,000: Rulebook (5th Edition), pp. 101, 116
- Warhammer 40,000: Rulebook (3rd Edition), pg. 278
- Warhammer 40,000: Rogue Trader (1st Edition), pg. 133
- White Dwarf 268 (US), "Assault on Holy Terra" by William King
- Galaxy In Flames (Novel) by Ben Counter
- A Thousand Sons (Novel) by Graham McNeill
- Prospero Burns (Novel) by Dan Abnett, pp. 31-41, 57-58
- The Outcast Dead (Novel) by Graham McNeill, Chs. 10, 11, 12, 13
- Vengeful Spirit (Novel) by Graham McNeill, Ch. 24
- The Purge (Novella) by Anthony Reynolds, Chs. 4, 6, 11
- Inquisition War (Omnibus) by Ian Watson
- Draco (Novel) by Ian Watson
- Deliverance Lost (Novel) by Gav Thorpe
- Harlequin (Novel) by Ian Watson
- Watchers of the Throne: The Emperor's Legion (Novel) by Chris Wraight, Chs. 4, 8
- Wolfsbane (Novel) by Guy Haley, Ch. 7
- Wolfblade (Novel) by William King, Chs. 4, 13, 17
- Inquisitor (Novel) by Ian Watson
- I Am Slaughter, Book 1 of the Beast Arises (Novel) by Dan Abnett, Chs. 3, 13, 15
- The Emperor Expects, Book 3 of the Beast Arises (Novel) by Gav Thorpe
- The Last Wall, Book 4 of the Beast Arises (Novel) by David Annandale, Ch. 1
- The Beheading, Book 12 of the Beast Arises (Novel) by Guy Haley, Chs. 9-17
- Dark Imperium (Novel) by Guy Haley
- Watchers of the Throne: The Emperor's Legion (Novel) by Chris Wraight, Chs. 4, 8
- Warhammer Community - Grim Dark Corners: Terra
- The Buried Dagger (Novel( by James Swallow, Chs. 1, 3