Solar System

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A general introduction to the neglected celestial bodies of humanity's home system in 40k.



It is the sun, yellow, G Class, with 5 billion years of life left under normal circumstances. General graveyard of heretics and their possessions (no pun intended).


Mining world. That's it. Literally. The lore is that long. However much ore is left after tens of thousands of years is a matter of debate.


An Imperial forge world. Before the Great Crusade it was ruled by the War Witches, whoever they are, but was brought under the control of the Imperium by the early Iron Warriors.

Earth/Holy TerraEdit

The capital planet of the Imperium, the homeworld of mankind and the most important world in the whole of the Imperium. Unless you are an astronaut, you are here.


Used to be ruled by gene-cults with a lot of growth vats before the Emperor set off uniting the Solar System. Refusing to be annexed and sending the envoy back as a somehow living sack of flesh, this caused big Emps sent the XVIth Legion(and co.) upon them, with the gene-cults finally saying "OK, we surrender, call off your wolves." As such, the Luna Wolves were christened.

Mars/Sacred MarsEdit

Home of the Adeptus Mechanicus, and the biggest forge world of all by several degrees of magnitude. Phobos is also a Mini Forge World / Defense Platform while Deimos got moved to Saturn, specifically Titan.


A gas giant Forge World, though the entire population is in orbit on one of the moons or in the various stations and docks that surround it. Jupiter is THE Imperial Navy's foremost shipyard and drydock. It only makes ships, though the planet is also ringed by a dense cloud of broken ships that are waiting to be scrapped and re-purposed into new materials. It is a hotly contested Imperial political debate as to whether Jupiter is soverign to the Mechanicum or the Imperium. They went totally green though, the hippies.

It once had a Forge Moon, Ganymede, that was used for experimentation on recovered Squat technology. However, the experiments went awry and the moon was declared lost forever and declared a quarantine zone. However, since Roboute Guilliman returned, the Grey Knights got off their asses and recovered the moon, allowing the Imperium to convert it into a Hub-Fortress for the supply of the Indomitus Crusade.


Though an inhospitable gas giant, the rings and many of the moons of Saturn were populated prior to the Great Crusade and formed a pocket empire called the Saturnyn Ordo that were occupied by some unnamed Xenos race. Given the Ordo's forces were called Void Hoplites, they were likely the Greeks to Terra's Romans.

The worlds were swiftly liberated by the fledgling Imperium and were absorbed fully shortly thereafter where they became one of the first recruiting worlds of the Solar Auxilia and formed a cornerstone of the Imperial Army.

At some point during the Horus Heresy, the Saturnyn Ordo was seemingly dismantled and the rings and moons of Saturn were designated a quarantine zone by Malcador. Access became heavily restricted as he forwarded his plans to create the Grey Knights under the veil of secrecy with standing order to destroy any unregistered ships that approach.

Later, the moons were ravaged by the Night Lords Legion during the Solar War as a prelude to the invasion of Terra. Though the depopulation of the planet probably aided in keeping the secrets of the Inquisition after the war ended, and the planet and its moons have remained an Inquisitorial stronghold ever since.

  • Titan - Homeworld of the Grey Knights chapter. Is itself orbited by Deimos, once the moon of Mars that has since been relocated. It now acts as the Grey Knight's own private Forge World.
  • Encaladus: Once upon a time this was the capital of the Saturnyn Ordo, where they signed the treaty with the Emperor and joined the Imperium. Is now the Palace-Fortress of the Ordo Malleus where many inquisitors have private estates.
  • Iapetus: Formerly home to a hold-out of anti-Imperial rebels who fought against the Death Guard and lost. Is now home to a naval fortress, although they serve the Inquisition and Grey Knights almost exclusively.
  • Mimas: Inquisitorial prison, holding the worst criminals kept in isolation and guarded by psychic wards, gun servitors and their own Stormtrooper regiment.
  • Tethys: Designated a Death World due to daemons trapped on the surface that are used as a training tool for aspirant Grey Knight Paladins who need to go to the surface and make a pilgrimage without wearing their armour. Canon differs on whether Tethys is also the location of the archive of the massively fortified Librarium Daemonica or whether it is located on Titan itself.


Uranus has no solid surface and its 27 moons were too small for permanent settlement (The largest: Titania is less than half the radius of Luna). Nevertheless, it was surrounded by a series of orbital cities populated by peaceful artisans called the Azurites. They built a stable warp route called the Elysian Gate allowing ships to bypass the normal Mandeville points in the Sol System.

The Azurites peacefully agreed to become absorbed into the Imperium of Man, but were assaulted by pirates who initiated what would later be called the Unheard War. The Azurites petitioned the Imperium for aid and a force of fifty Imperial Fists were sent to provide support. The Space Marines quickly broke the pirate invaders within twenty minutes of battle, but as a parting gift, the pirate fleet fired boarding torpedoes loaded with psykers infected with a psychic plague called the Screaming, which was contagious through sound and caused its victims to mutate horribly and die screaming.

As the only vaccination against the plague, the Imperial Fist forces purposefully deafened themselves and fought through the waves of mutated citizens to the station reactor and initiated a self destruct, preventing the plague from spreading any further. For their sacrifice, the Emperor ordered the Bell of Lost Souls to ring for the first time.

Despite the small size of its moons, they were heavily fortified during the Horus Heresy and acted as Rogal Dorn's "Second Sphere" of defense during the Solar War. These forces were overwhelmed by Perturabo and a fleet of over 4,000 vessels brought through the Elysian Gate. The Imperial Fist fleet avoided engagement by sniping as many ships as they could from their fortresses and managed to hold off against the sheer number of invaders for around 36 hours before retreating, saving themselves for later engagements around Jupiter and buying more time to withdraw to Terra.

Uranus was only reclaimed during the Great Scouring.


Neptune's moons were settled during the Age of Terra some point between M15-M18, though the population devolved into hideous mutants.

The IXth Legion were given the task of bringing them to compliance, and fought a bloody war through the tunnels of its moons that cost them 12,000 men, though due to the beneficial quirks of their gene-seed they were able to replenish those numbers directly from the conquered mutant population.

The moons of Neptune were frequently infiltrated by chaos or genestealer cults at later periods.


The dwarf planet Pluto is the site of several relay stations that allow for early detection of incoming vessels to the solar system. It (along with Uranus) also houses the Khthonic Gate warp gate allowing ships to bypass the normal mandeville restrictions, making the location a stragetic asset which is heavily fortified.

Prior to the Siege of Terra, Rogal Dorn seems to have killed Alpharius during the Battle of Pluto in the Horus Heresy, though this was simply a prelude to the proper Solar War.

A massive fleet of Sons of Horus swept in through the Khthonic Gate and successfully landed on the fortified moon of Kerberos, and managed to successfully turn its guns on the loyalist defenders. Though Sigismund had predicted this outcome, and ordered a full retreat while his Tech Priests initiated an overload destroying the moon outright, scattering the traitor fleet and allowing Sigismund to turn his fleet around and counter-attack. With few options available to the traitors, Horus Aximand assaulted Sigismund's flagship and managed to capture it, although was bested in personal combat before Sigismund managed to escape and withdraw the remainder of his fleet to Terra, having bought the loyalists several days of time.

The Planets, Systems, Regions and Sectors of the Galaxy
Imperial Homeworlds: Holy Terra - Sacred Mars
Primarch Homeworlds: Baal - Barbarus - Caliban - Chemos - Chogoris - Colchis
Cthonia - Deliverance - Fenris - Inwit - Medusa - Nostramo
Nocturne - Nuceria - Olympia - Prospero - Ultramar
Planets: Armageddon - Bakka - Cadia - Catachan - Ganymede
Hydraphur - Krieg - Kronus - Sacris - Sanctuary 101
Scelus - Tanith - Tartarus - Vigilus - Vraks - Zayth
Daemon Worlds: Plague Planet - Sortiarius
Systems and Regions: Ghoul Stars - Halo Zone - Jericho Reach - Kaurava System
Solar System - Stygius Sector - T'au Septs - Taelus System
Types of Worlds: Agri-World - Craftworld - Daemon World - Death World - Eldar World
Forge World - Fortress World - Hive World - Tomb World