Sol System - Notable Planets: Mercury (Mining World) - Mercury is a small, Dead World and Mining World that orbits very close to Sol. Despite its unforgiving conditions, shoal facilities operate in Mercury's orbit. In ancient days there was a city known as Cytheron on Mercury, which produced the advanced defensive Cytheron Pattern Aegis shield devices used by the elite Deathwing Astartes of the ancient Dark Angels Legion during the Great Crusade and Horus Heresy. During the Horus Heresy, Alpha Legion infiltrators worked with anti-Imperial scavenger clans in the area.Venus Industrial World - Venus is an inner planet of the Sol System, and the second closest to Sol. During the early stages of the Great Crusade, Venus was conquered by the Iron Warriors Space Marine Legion during the Mehr Yasht Campaign. The planet was dominated by War Witches who fielded armies of Litho-Gholem. After the formation of the Imperium, Venus would play host to a wide variety of luxury resort orbitals, all intended to help the elite of the Sol System find respite and relaxation.Terra (Hive World / Throneworld) - Terra is the Throneworld of the Imperium of Man and the original homeworld of Mankind and the Emperor. It is the most sacred and revered place in all the million worlds that comprise the Imperium. Terra is an ecumenopolis, a single cityscape straddling the entire planet, with its vast hive cities covering the entirety of its surface. It is home to hundreds of billions of people and visited annually by tens of billions more seeking to complete religious pilgrimages to the world that their God-Emperor calls home.Luna (Dead World / Civilised World) - Luna, Terra's only natural satellite, is a densely settled Civilised World of the Imperium. Its massive population lives in great cities built deep below the lunar regolith. Luna is most famous for the gene-laboratories where the Emperor of Mankind made the genetic breakthroughs that would ultimately culminate in the creation of the large numbers of Astartes who comprised the Space Marine Legions of the late 30th Millennium. Luna also boasted a large collection of orbital dockyards for starship construction and maintenance, although these were destroyed during the Horus Heresy.Mars (Forge World) - Mars is the greatest Forge World of the Imperium of Man, producing vast numbers of weapons, vehicles and other technology for the Imperial war efforts throughout the galaxy. Mars is also the ancestral home of the Adeptus Mechanicus and their Cult Mechanicus.Phobos (Orbital Fortress) - Phobos is Mars' only remaining natural satellite. A small moon only 11 kilometres in diameter, Phobos' surface is completely covered in weapons-studded fortifications and is used as an orbital fortress that protects the Red Planet and its equatorial Ring of Iron.Ceres - Ceres is a small dwarf planet located within the Sol System's inner asteroid belt. During the Horus Heresy era, Ceres was home to vox relay and communication stations that helped with communications between the inner and outer reaches of the system. Ceres was also home to various orbital habitat stations who were engaged in the industrial mining of the Asteroid Belt.Jupiter (Gas Giant Mining World) - Jupiter is a massive gas giant and the fifth planet of the Sol System. The orbital space docks and workshops that orbit Jupiter are home to massive Imperial Navy shipyards controlled by the Tech-priests of Mars. During the time of the Horus Heresy, the moons of Jupiter were known to possess habitats used by the workers of the shipyards in Jupiter's orbit, all of which were powered by the constant stream of radiation emitted from Jupiter. It was in orbit of Jupiter that the infamous Word Bearers warship, the Furious Abyss, was constructed, before it turned its guns upon its own shipyard in order to maintain the secrecy of its existence.Ananke - A small moon of Jupiter known to have had habitats on its surface by the time of the Horus Heresy.Iocaste - This moon of Jupiter is known to have had habitats on its surface by the era of the Horus Heresy.Europa - Located within the range of Jupiter's Galilean moons, Europa had been geo-engineered into an ocean-moon by the time of the Horus Heresy.Io - The seething orange mass of the moon of Io is home to a uninhabitable volcanic wasteland.Ganymede (Aquila Adamant) - One of the four greater Galilean moons of Jupiter that was known to have had ancient Mechanicum habitats on its surface during the Great Crusade and Horus Heresy eras and served as the central hub of the massive complex that made up the orbital Jovian Shipyards. Later, it was transformed into a Warp-tainted wasteland created by the malfunction of experiments designed to test the limits of Squat Warp-coil technology. In the Era Indomitus, Ganymede was transformed on the orders of the Primarch Roboute Guilliman into a massive hub-fortress of the Officio Logisticarum called Aquila Adamant. Its purpose is to supply, support, and archive the actions of the Indomitus Crusade's fleets and battle groups as they advanced across the galaxy.Thule - Thule is a small, irregular asteroid moon of Jupiter that served as the clandestine shipyard for the construction of the Furious Abyss and was destroyed by Renegade members of the Mechanicum during the Horus Heresy.Callisto - Callisto was a Galilean moon of Jupiter known to hold residential orbitals above its surface by the time of the Horus Heresy.Saros Station - Saros Station was a void station that orbited Jupiter during the time of the Great Crusade and Horus Heresy. This space station resembled a vast spindle bathed in a crimson glow which made it appear as if it were a crystal chandelier that had been severed from its mounting and cast free into the void. Unlike the majority of the gas giant's other industrial and colonial space stations, Saros had been a resort platform before the Horus Heresy, where the Jovian elite found respite as well as diversion from the work of the Jovian system's orbital shipyards and manufactoria. It was said that only the Venus orbitals could surpass Saros Station in luxury with its avenues of gold and silver, null-gardens, auditoriums, and the finest opera house outside the Imperial Palace itself.Kadal - Kadal was the name of a Jovian satellite munitions fortress during the time of the Great Crusade and the Horus Heresy. During the Heresy, Kadal was the site of an Alpha Legion-instigated anti-Imperial revolt and was subsequently destroyed during the Solar War.Saturn (Gas Giant) - Saturn is a massive, ringed gas giant and the sixth planet of the Sol System. Unlike the rest of the worlds in the Sol System, Saturn never hosted a large human population, due in part to xenos activity, thus making it the perfect candidate to house the newly-created Inquisition when it was first established at the end of the Horus Heresy. The moons of Saturn serve as the location for a massive complex of military bases and orbital shipyards maintained by the Inquisition. All of these areas are off-limits to anyone who does not serve or have clearance from the Holy Ordos of the Inquisition. Any unidentified vessels nearing Saturn are promptly destroyed by its sophisticated orbital defences.Titan (Inquisition Fortress World / Space Marine Chapter Homeworld) - Titan is the largest moon of the gas giant Saturn and the largest moon in the Sol System. It is wholly controlled by the Grey Knights Chapter of psychically-active Space Marines who serve as the Chamber Militant of the Inquisition's Ordo Malleus. The fortress-monastery of the Grey Knights is based on Titan, and is carved entirely of basalt.Deimos (Forge World) - Deimos was previously the second moon of Mars and served as a small Forge World with smog-ridden manufactoria that produce weapons and armour. When Malcador the Sigillite created the Grey Knights during the Horus Heresy, the moon was displaced from realspace and into the Warp alongside Titan itself. Several standard centuries after the Battle of Terra it reappeared, its orbit relocated to circle Titan by way of unknown arcane technologies. It is now the primary source of the wargear and vehicles used by the Grey Knights.Mimas (Inquisition Prison World) - Mimas is the closest major moon to Saturn, marred by an immense impact scar that covers a quarter of the surface. This crater houses the Inquisitorial Prison Complex which contains the worst criminals hunted by the Inquisition, who are kept in isolated cells with psychic wards woven into the walls and guarded by Gun-Servitors and an Inquisitorial Storm Trooper regiment.Encaladus - Encaladus houses a citadel of the Inquisition and is a vast palace from which Lord Inquisitors of the Ordo Malleus hold court, and also the world where many of these Lords maintain their personal estates. The primary citadel used by the Inquisition is known as the Encaladus Fortress. In the libraries of that fortress, there are countless volumes of forbidden lore on the subject of Chaos and daemons. The Encaladus Fortress also incorporates the Admiralty Spire, where the empire of Saturn's ancient rulers signed their treaty with the Emperor during the Great Crusade to join the Imperium of Man.Tethys - Tethys is the site of the hidden archive of the Librarium Daemonicum, access to which is restricted to Lord Inquisitors. Tethys is home to a number of daemons trapped beneath its surface. One of the set trials for all aspiring Paladins of the Grey Knights is to survive on its surface without their Power Armour.Iapetus (Imperial Navy Fortress) - Iapetus is the furthermost major moon in orbit of Saturn, and home to a vast naval fortress and series of dockyards that serves the various strike fleets of the Grey Knights Chapter, along with the starships requisitioned from Battlefleet Solar by the Inquisition. As it is under Inquisitorial command, Iapetus serves as the only reliable means of getting into and out of the rings of Saturn. Iapetus was a stronghold of the Ringers, the culture that occupied parts of the Saturnian system before the coming of the Emperor and the Imperium during the Great Crusade.Uranus (Gas Giant) - Uranus is a massive gas giant and the seventh world of the Sol System. Though never habitable, it is home to orbiting human colonies, most notably the Azurites, a peaceful community of artisans who made their livings through scavenging. The Azurite population was largely wiped out during the Great Crusade during the so-called Unheard War when their population became infected by a Warp-spawned disease known as The Screaming which began to mutate them into daemons. Though the Imperial Fists Legion was despatched to provide aid, the Azurites were annihilated by the Astartes' need to prevent the plague from spreading across the Sol System. The moons of Uranus are now used mostly for mining by the Imperium. By the time of the Horus Heresy, Uranus' moons and close orbitals had been repopulated by new human colonists.Ariel - One of Uranus' major moons, Ariel is home to Imperial mining operations.Neptune (Gas Giant) - Neptune is a massive gas giant, the eighth and furthest major planet from Sol. Neptune was first colonized by humanity during the era known as the Age of Terra. By the time the Emperor reconquered Neptune for the Imperium during the Great Crusade, its inhabitants had been transformed into mutants by the isolation from Terra and the harsh environment, which caused them to be destroyed by the forces of the Emperor.Pluto - Pluto is a small dwarf planet located in the outer rim of the Sol System. During the Great Crusade era, Pluto was home to relay stations that were responsible for warning Terra of any imminent invasion. During the Horus Heresy, the world and its accompanying moons was the site of a major Alpha Legion attack in what became the first major engagement of the Solar War.Charon - Charon is the largest natural satellite of Pluto.Styx - Styx is a natural satellite of Pluto.Nix - Nix is a natural satellite of Pluto.Kerberos - Kerberos is a natural satellite of Pluto and is used as a heavily armed orbital fortress.Hydra - Hydra is a natural satellite of Pluto and houses an Astropathic-relay station.Sedna - Sedna was a planetoid-sized trans-Neptunian object of xenos origin located within the Sol System's inner Oort Cloud. During the early Great Crusade eight Space Marine Legions fought against an unremembered xenos species on the dark surface of Sedna, finally leaving the entire Sol System in human hands for the first time since the start of the Age of Strife.