BoLS logo Tabletop, RPGs & Pop Culture

40K Loremaster: Cradles of Treason – Homeworlds of the Chaos Primarchs

10 Minute Read
Mar 13

Today Loremasters we ask the age-old question – Nature or Nurture; as we examine the homeworlds of the Traitor Primarchs.

The Primarchs were all whisked away from their growing tubes deep in the Emperor’s lab on Terra and hurled across the galaxy. Here are the homeworlds of those who would turn their backs on their father.

Cthonia – Horus

Cthonia was the world on which Horus landed after being stolen from the grip of the Emperor.

This planet allegedly existed in one of Earth’s closest neighbouring systems. Being within reach even for non-warp spacecraft, Cthonia had been colonised, built upon, tunneled and mined probably since the dawn of space travel. As such, all natural resources had been stripped away and used up millennia before, and the ancient mining technology had long since been rediscovered and removed by the Adeptus Mechanicus of Mars. The planet that remained was largely redundant and abandoned, completely riddled with catacombs, crumbling industrial plants and exhausted mine-workings. The planet was notorious for the vicious gangs and slums.

After the arrival of the Emperor, the Space Marines of the Luna Wolves Legion were created using the human inhabitants of the violent gangs inhabiting the planet’s Hives.

The planet was destroyed after the Horus Heresy.

Nuceria – Angron

Nuceria was a brutal, unforgiving world run by cruel slavemasters from the city of Desh’ea that forced their subjects to battle in gladiatorial arenas. The aggression-enhancing technology known as the Butchers Nails was a key part of this process. The young Angron was captured and forced to take part in this cruel game until he led a slave revolt. However, at the height of the battle against the slavemasters, he was teleported away by the Emperor, something that infuriated the Red Angel. In the aftermath of Angron’s unwilling departure from Nuceria, his comrades were defeated and massacred by the slavemasters, which Angron referred to as the “High-Riders”.


Many years later, during the Horus Heresy, Angron returned to Nuceria alongside the Word Bearers‘ Primarch Lorgar. Upon his return he discovered that the slavemasters had told the planet’s populace that he had fled in the final moments of his slave revolt. Infuriated at this lie, Angron ordered the purge of all life on Nuceria, something the World Eaters and Word Bearers brutally carried out. During the purge, a large fleet of Ultramarines led by Roboute Guilliman himself arrived in orbit over Nuceria and engaged the Traitor forces, eager for revenge for the Battle of Calth.

Nuceria is now a Dead World.

Prospero – Magnus

Prospero was a desolate, dark planet and was chosen by its inhabitants because of its distance from Terra. Mutants and Psykers lived in reclusion and study, and Magnus fit in well with this group due to his incredible psychic potential.

In the end, the only good thing about Prospero was its remoteness, which made it easy to hide on. It had one major city, Tizca, a gleaming city of white marble, with spires reaching into the sky. It was situated on the most central of the many mountains of the planet, nourished by underground hydroponics and techno-psychic collectible arrays providing sustainable energy. All the towers were gleaming and there were soaring obelisks and towering pyramids.

When Magnus arrived, he crashed into the central plaza of the city. The city was very vulnerable from attack from above, but no one seemed to notice this until Leman Russ came and bombarded the planet. He attacked the planet with extreme viciousness and devastating results, slaughtering all he could find. In the end, after a grueling duel between the two primarchs, Magnus cast spells that took all of the great city, his marines, and his precious libraries to a new Homeworld, the Planet of Sorcerers.

Later in the Heresy, the White Scars under Jaghatai Khan arrived to investigate what had transpired. They found no survivors from either side and the vengeful ghosts of slain Thousand Sons wandering the ruins of Tizca. The Khan was confronted by a shade of Magnus, who discussed both of their successes and failures and may have been tempting his brother to join the forces of Chaos. After refusing Magnus, Jaghatai then refused the newly arrived Mortarion and the two Primarch’s battled as their fleets clashed in space. After a brief but intense battle between Astartes warships, the Death Guard disengaged.

In the 40th Millenia, Magnus and Ahriman used great sorcery to move the Planet of the Sorcerors into the Prospero system, and out of the eye of Terror. This teleportation was one of the events leading to the creation of the Great Rift.


Barbarus – Mortarion

Barbarus was a Feral World which orbited near its dim yellow sun. The atmosphere was thick with virulent gases and a constant fog was spread across the planet. This made it a very dark, dismal place of night with short, shadowy days. Only below the fog could humans survive, in the valleys and low plains.

Beings immune to the toxic fog survived within the toxic cloud and built great grey keeps in the mountains. The higher beings began to use the humans as slaves and spread terror among them, what these creatures were is not certain. After landing on the world, Mortarion eventually led the citizens of Barbarus in a revolt against the mountain ruler, toppling them before joining with the Emperor.

After the Horus Heresy and the commencement of the Great Scouring, the loyalists subjected all worlds associated with the Traitor Legion’s to Exterminatus. Barbarus was among the worlds destroyed by the vengeful Imperium with Virus Bombs. Another source states that it was destroyed by the Dark Angels shortly before the Siege of Terra with Cyclonic Torpedoes.

On the surface of Barbarus was the Wall of Memory, where the names of every Space Marine of the Death Guard legion killed during the Great Crusade were carved.

Chemos – Fulgrim

Chemos was settled long ago as a mining world but was isolated from its neighbours by Warp Storms during the Age of Strife. The problem was that the resources of the planet were running out. The planet was not producing enough food even for its own population. Eventually, it fell to a group of fortress factories to produce all the resources. All people had to work every hour of the day, working the vapour mines and synthesisers. Recreation, art and leasure were sacrificed for survival. Because of the nebula clouds surrounding Chemos, it experienced neither day or night but was in a perpetual grey haze.

When Fulgrim crashed into the planet, he was taken in by one of the planetary police. He grew quickly and within fifty years he was ruler of the planet. Fulgrim managed to get the planet going again, re-opening old mines and farms. Resources started flowing through the planet again. It continued to grow after the Emperor arrived and re-opened trade in the sector.

The Fortress Monastery of the Emperor’s Children was located at the centre of Callax, one of the major cities on Chemos. After the Horus Heresy, it was bombed from orbit by Imperial forces and then quarantined by the Inquisition. The holy scripture the Chemosian Cantos was written during the final hours of the planet, and is still revered by human slaves of the Emperor’s Children.

During the final stages of the Horus Heresy, Chemos was left undefended by the indifferent Emperor’s Children and was destroyed from orbit by the Dark Angels.

Colchis – Lorgar

Colchis was a massive world, three times larger than Terra. It took 4.8 Terran years to orbit its sun and 170.4 Terran hours to rotate once around its axis, giving it an extended day-night cycle to which humans could not adapt; thus, the Colchisian civilizations developed a unique method for keeping track of time. Mountains and deserts dominated its dry land and civilisation clustered along coastlines, relying on water and air travel between settlements. Its capital city-state was Vharadesh, the City of Grey Flowers.


Life on Colchis was often harsh outside of the cities which were all controlled by a religious institution known as The Covenant. Slavery was rife, and Desert nomads who dwelt outside of these cities were dubbed The Declined and seen as damned by the Great Powers.

It was originally a technologically advanced world but it regressed to a feudal state, prior to the arrival of Lorgar. Ancient ruins dotted the landscape and derelict starships littered its orbit. At the time of Lorgar’s arrival the planet was dominated by the Covenant of Colchis. After being raised by Kor Phaeron, Lorgar was able to lead a rebellion that overthrow the Covenant and conquered the planet.

After his discovery by the Emperor, Lorgar brought the planet into the Imperium, granting it access to advanced technology and society. Under Lorgar’s brief rule the planet prospered but when the Emperor took Lorgar away, the planet plummeted back to a feudal state. Imperial traffic avoided Colchis not only for its lack of orbital infrastructure but also due to rumours that the area was unreliable after the disappearance of the 2,188th Expeditionary Fleet.

When the Ultramarines returned to Colchis to purge it after the Horus Heresy they found a collapsed world. All of the industries were destroyed and people barely clung on to life. The Inquisition ordered the cleansing by the use of cyclonic torpedoes, disrupting Colchis’s delicate geological structure, and thereby triggering a catastrophic explosion that annihilated the planet. At the time the Mark of Calth had reached 219,479.25.03 (approximately 25 years).

Olympia – Perturabo

Olympia was originally a rugged, mountainous world whose population was concentrated within many city states, spread across the planet’s surface. The planet had vast amount of stone available and as such large fortresses were built, and controlling the paths through the mountains and the high ground was very important to military security. One of the city states, the home to the PrimarchPerturabo, was named Lochos. The leader of Lochos, known as the Tyrant of Lochos, dominated the region. When The Emperor arrived, he granted Perturabo a Space Marine Legion. He used this new force to depose the Tyrant of Lochos and take control of the planet. He recruited from the population of Olympia and joined The Emperor on his Great Crusade.

Much later, just prior to the Heresy, Perturabo, already shaken by the Sak’trada Deeps Campaign, learned that Olympia was in rebellion against him. Governor Dammekos had passed away, and in the power vacuum left after his death the Olympian lords had resumed their politicking and bickering. Perturabo was devastated, and returned to cleanse his world with a terrible rage. He gave the planet’s occupants the choice to enact decimation, selecting 1 in every 10 of their own to die, or face extermination and enslavement if they refused[5]. Each city was cleansed street by street, leaving few alive. By the end, Olympia was in slavery and over five million were dead. Some Iron Warriors themselves to take part in the carnage, and they too were struck down by their brothers. Great pyres burnt in the skies of Olympia that day.[1] The Iron Warriors became aghast at the genocide they had unleashed, and Perturabo knew his father would never forgive him. Horus on the other hand was more than willing to forgive the Lord of Iron, and even praised him for his decisive action. This helped turn the Iron Warriors to betray the Emperor.

After the failure of the Horus heresy and Horus’s death, the Iron Warriors retreated back to their strongholds. Olympia held out against a combined Ultramarines and Imperial Fists attack for two years, but ultimately when it was determined the Loyalists would defeat them, the Iron Warriors triggered their own missile stockpiles.

The resulting explosions turned Olympia into a vast barren wasteland and from that day on, the world was declared Perdita by the Imperium.

Nostaomo – Konrad Curze

Nostramo, on the inside edge of the Ghoul Stars, was a planet of perpetual darkness, covered in clouds of pollution and a perpetual solar eclipse. Only the planetary elite could afford artificial illumination. Murder, extortion, and theft were rampant, while the elite oppressed the vast underclass of foundry workers with hired thugs, the closest approximation the planet had to law enforcement. Violence, both interpersonal and suicide, kept the population in check.

Nostramo’s geology contained priceless wealth, particularly huge quantities of naturally occurring adamantium. The mineral trade made Nostramo great amounts of wealth, but at the cost of vast chemical and metalworking facilities scarring the landscape, throwing up the toxic clouds that perpetually darkened the skies.


In one year, the Night Haunter massacred the planets criminal overlords in a reign of terror. By the end of the year, crime had fallen to near-zero as the people lived in fear of the “Night Haunter”. The Night Haunter became the city’s first monarch. The few nobles who survived by swearing loyalty to him became his mouthpieces. He would rule with a fair and even hand, but any who transgressed would die.

At first, the people felt they were free to speak their minds again, no longer subject to the gruesome punishments of the Night Haunter, but replacing his autocracy with the Administratum soon became a return to the old ways.

The bureaucratic corruption of the Administratum was bad enough, but the Emperor’s arrival robbed the Nostramans of their ignorance. They now knew that there were better places in the galaxy than this one and they would never be able to see them. The only class of people who would ever get off-world were the new breed of violent criminals who were selected to fill the ranks of the Night LordsSpace Marine Legion.

The next time the Night Haunter returned to Nostramo would be the last. Word had reached the legion that Imperial governor Basileus’s regime allowed crime to run rampant once again. The Night Haunter’s entire fleet arrived in orbit and aimed their weapons at their home world. Countless lance barrages and orbital torpedoes pummeled the surface. The bombardment reached the planet’s core, possibly through a weakness left in the crust by Curze’s landing or the extensive adamantium mining, and the planet burst apart.

UNKNOWN – Alpharius

There are no records of the homeworld of Apharius and he never spoke of his early life.

~Guard this knowledge well, else the Ruinous Powers consume you as well.

Latest News From BoLS:

  • Advertisement
  • 40K: Necromunda Gets More Lore For Your Narrative Core