During Year 6 when the Darkness Fleet arrived, our enemies had overpowered us at several key locations in our Solar System. As a result, we have lost contact with several allies and lost significant territory. Until we are ready to face the Darkness, those locations are now off limits.
During the Golden Age, numerous great cities such as New Pacific Arcology were built on Titan and became the envy of the rest of the Solar System. These cities were intended to be entirely self-sustaining due to the inhospitable nature of Titan’s surface. Settlements on Titan were known to trade with other nearby worlds, such as Hyperion. Scientists also flocked to Titan to escape the stifling influence of organizations like Clovis Bray and carry out independent research. The moon was never terraformed by the Traveler, although 97% of New Pacific Arcology’s residents hoped it would be chosen soon.
Titan was one of the first places in the Solar System to detect the arrival of the Darkness, and consequently one of the first places to experience the Collapse. A deep-space probe launched by a team under Dr. Shanice Pell encountered an inexplicable anomaly before losing contact with New Pacific Arcology. Not long after, the anomaly was determined to be such a threat that the entire planet was evacuated. The evacuation may have caused the Darkness to bypass Titan, as none of its structures bear visible battle damage, only wear and tear from a lengthy period of neglect.
The moon’s cities remained completely abandoned for centuries, slowly decaying and sinking into the methane ocean. Guardians such as Cayde-6 used Titan as a rest stop during journeys to and from the outermost reaches of the system. Shortly before the Red War, however, a new Hive sect colonized Titan’s ruins. When a group of newly-Lightless Guardians under Commander Zavala fled to Titan, hoping to use it as a secret base from which to launch a counteroffensive against the Red Legion, they found New Pacific Arcology heavily infested and nearly gave up on their plan. Worse, Fallen from the House of Dusk had followed the Guardians from Earth, and began feuding with the Hive. Fortunately, thanks to the timely arrival of The Guardian, the support rigs outside the Arcology proper were sufficiently cleared to allow Guardians to secure the command center and City jumpships to refuel there.
Around the time of the Almighty’s descent upon The Last City, the Pyramids themselves had finally reached the outer Solar System. After corrupting Pluto, Neptune, and Uranus, the Pyramids set their sights on Titan.
A month after the arrival of a Pyramid on Io, another Pyramid arrived on Titan, holding position outside of the New Pacific Arcology. It was the first of the newer Pyramids to start deploying Pyramid Scales on the Arcology, antagonizing the Hive and Fallen there. They eventually overtake the area.
In the final days of the Golden Age the Traveler was in the midst of terraforming Io when it detected the Darkness approaching; The Traveler began to move to Earth in a defensive posture, leaving Io half-completed and flooded with the Traveler’s formatted energies. As a result of this, the Ionian climate and geography do not support traditional agriculture, meaning that some remnant of Io’s original atmospheric composition prevented the full growth of plants. The moon is still charged with the Traveler’s pure energy, which lingers in the atmosphere of the moon, visible from orbit. Echo Mesa, a mountain on Io,has become a popular pilgrimage site for Guardians. The Mesa overlooks a crater where the Traveler left behind a mysterious city-like structure.
The terrain of Io is covered in fossils, many of which closely resemble enlarged versions of ancient Earth organisms such as trilobites, ammonites and dinosaurs. It is unknown whether these fossils are a by-product of the Traveler’s paracausal terraforming, or whether they point to some unrecorded history of transplantation between Earth and a more habitable Io in the distant past.
During the Red War, Io became a warzone for Guardian, Red Legion, Vex and Taken forces. When the Red Legion arrived in the solar system they set up at Terrabase Charon, on Echo Mesa and were met with resistance from the Vex and Taken forces there. Io was the final place that the Traveler influenced with Light in the Solar System, and as such is sacred ground to Warlocks. During the conflict, The Guardian travels to Io on Zavala‘s orders to find Ikora. After locating the Warlock Vanguard leader, Ikora sends the Guardian on several missions into a Cabal research base, ultimately revealing the Red Legion’s plans for the Traveler and the Light. The Cabal were mining out the remaining Light energy from the Traveler, which attracted the forces of the Taken and forced the Cabal to evacuate. During the Guardian’s time on Io, they also meet Asher Mir, an Awoken scientist fixated on the Vex, along with their activities on the planet.
A Vex structure known as the Pyramidion is found there, which was fought over by the Taken in another attempt to infect the Vex network like Oryx had with the Vault of Glass. The Pyramidion is described by Asher Mir and Ikora as a “conversion engine”, responsible for converting Io into a Vex Machine World and is believed to be one of many entry points into Vex space, where one of their Axis Minds performed experiments on captured Guardians. The Pyramidion is only accessible during the Curse of Osiris story mission, Deep Storage and in the strike, The Pyramidion.
A hidden Warmind vault, JYS-2, was buried beneath Io’s surface and inadvertently uncovered by one of the Cabal’s drills. An unidentified active AI – implied through various details to be Rasputin – was still using the facility. Instead, it communicated via pre-Golden Age music and philosophical quotations, which proved to intrigue the Vex. This can be observed in the Adventure Arecibo.
Following the destruction of The Almighty, a Pyramid touched down on the moon, disabling Rasputin and positioning itself above the Cradle, where a Tree of silver wings lay inside. It is unknown if the tree was always there or if the Pyramid spawned it.
Following its transformation into a garden world by the Traveler, the planet was inhabited by humanity during the Golden Age. At this time, the planet was covered in grasslands and trees with pink leaves. During the Collapse, the Vex undid this transformation and completely changed Mercury into a Machine World within days of their arrival, using “Lighthouses” to flood the planet with Radiolaria to facilitate its transformation. Dendron, Root Mind arrived in a massive Vex construct to begin seeding the planet with Vex architecture and poisoning all life with Radiolarian fluid. Eventually the Infinite Forest was created to serve as the Vex’ simulation farm, with Panoptes, Infinite Mind at its heart. The Sun itself, as seen on the planet’s surface, appears to be massive in size yet not blindingly bright—a possible result of Vex engineering.
Though much of Mercury is dominated by the Vex, others have managed to visit the planet, including the Cult of Osiris who maintains a camp there in the form of The Lighthouse. Flawless champions of the Trials of Osiris are permitted to visit the Lighthouse where they can find stores of Glimmer and other treasures, although the only rewards available are the ones in the chest at the edge. The Sunbreakers have their Forge here as well and the Cabal built an outpost at Vertigo, but have since mysteriously disappeared.
When Saint-14 tried to track Osiris on Mercury, Osiris’s trail caused him to get lost in the virtual expanse of the Infinite Forest. The Titan faced the Vex for several centuries, destroying thousands of them. Eventually, the Vex created an Axis Mind specifically designed to drain his Light. Though he destroyed the Mind, it succeeded in its mission by mortally wounding the legendary Titan and draining his Light. Out of respect, the Vex laid Saint-14’s body to rest in a tomb in a Simulant Future guarded by Hagios, Reverent Mind (Hagios meaning Saint) and surrounded by the melted shells of all the Vex he killed as a memorial to the grief he gave them. In Season of Dawn, his fate was altered by The Guardian, resulting in his eventual return to the City.
After Dominus Ghaul‘s death, the Vex began to gather on the planet. Osiris discovered that Panoptes had simulated a future where the Vex would achieve total victory in the solar system and wipe out all other life. Vex from the past and future were converging on this timeline to carry out their plan, but were foiled by the Guardian. It is seen during the Vex’s campaign, the Cabal had also sent troops by the order of Val Ca’uor to the fields of glass where they would attempt to secure technology from the Vex but become bogged down in an attrition war.
It is unknown how Mercury’s conversion to a machine world, and partial fragmentation have harmed the consciousness within it. It is also heavily implied in the Dust lore book that it is the Nine who engineered the cut-off of the City’s satellites and defenses right before Ghaul’s surprise attack, in order to learn how to manipulate Light from him. The Nine also mention how it was “punished” for this act, possibly being its fragmentation at the hands of the Almighty.
A month after the Almighty’s destruction at the hands of Rasputin, a Pyramid arrived on Mercury in similar fashion to its counterpart on Io. From its position, the Pyramid blotted out the Sun and shrouded the Fields of Glass in its shadow.
A harsh and deadly environment, Mars is now a desert world frequently plagued by dust storms. The Cabal forces have a presence on the planet in the form of their Exclusion Zone, as do the Vex, who are at odds with the Cabal. An indelible sign of the Cabal presence on Mars is the moon of Phobos, which has had its orbit dramatically altered by Cabal planetary engineering; it now fills a significant part of the sky. Even more disturbing is the discovery of large “planet-cracking” munitions among the Cabal’s already devastating arms. There is some degree of conflict as humanity tries to reclaim its former glory.
With the coming of the Traveler, rain washed over Mars, and it was here that humans first encountered the spherical entity. Once, populating Mars had been nothing more than a dream for humanity but after its terraforming, a thriving metropolis named Freehold came to dominate the skyline – a bastion of human life in the red dunes. The Clovis Bray corporation had a major presence in Freehold, in addition to setting up their own private facilities, such as one in the Hellas Basin which acted as a tourist attraction and a site for research into Exo and Warmind technology, as well as the location for the core of the Warmind Rasputin.
With the coming of the Darkness, nearly all of Freehold was “swept away” and the sand claimed what remained. Today, Freehold lies buried beneath a mountain of sand, and its once-soaring skyscrapers are only visible.
Mars would be subject to incursions from multiple alien races, being the Cabal, the Vex, and the Hive. The former two would find each other at odds in an attrition war in Meridian Bay, the area surrounding Freehold, with the Cabal vying to mine resources and study the Vex artifacts and structures in the area, which include the massive gate to the Black Garden. A Hive sect known as the Grasp of Nokris would attempt to invade the Hellas Basin, only to be frozen in ice by Rasputin’s defensive SIBERIAN ENTROPY protocol for the years to come.
Mars was once ruled by the Awoken.
When the Red Legion arrived in Sol, breaking the Cabal-Vex stalemate in Meridian Bay was one of its priorities. The Vex are hard-pressed and have lost multiple gates, including the Black Garden gate. The whole of Meridian Bay is now under total Red Legion control.
With the awakening of the Traveler at the end of the Red War, the ice caps on Mars began to thaw, extending to the iced-over Hellas Basin. This would also thaw the invading Grasp of Nokris, prompting Rasputin’s newly-awakened core intelligence to deorbit Warsats as a defensive measure, inadvertently attracting a defeated Red Legion looking to scavenge technology to strike back at the Guardians who denied their victory.
Two years later, a Pyramid would arrive on Mars, mirroring one of its counterparts which arrived on Io a month earlier. There was recently a signal that was coming from a device in the Clovis Bray Facility, Guardians went to investigate to find an individual’s journal who’s name is Helsom, Ana describes him as a Xenoarchaeologist who believed in possible contact with extrasolar species and humanity, she contemplated on if he ever found what he was looking for, he remained on Mars since the Collapse happened.