Nessus

"Lush with giant twisted trees, deep caverns, waterfalls, and silver swamps, the origin of this planetoid remains unknown. What is clear is that the Vex have nearly transformed the entire planetoid into a Machine World, above and below the surface. For those Guardians willing to brave the dangers and explore the myriad of mysteries, treasures beyond the imagination await."

- Website description

7066 Nessus is a Centaur minor planet with an irregular orbit. At perihelion, Nessus is closer to the Sun than Uranus; at aphelion, Nessus moves into the Kuiper belt, It is a place where Light is scarce.

Golden Age
During the Golden Age, the Colony ship Exodus Black crashed on Nessus on its way to Kepler-186. They were surprised by Nessus actually being where it is as it shouldn't be there, the ship's crash was due to the result of the Orbiting Centaur's added six dimensions to it's four dimensional space. They were all lost in their sense of Time, past and future went hand and hand for them. All of its colonists and crew were subsequently either captured and experimented on (such as stealing the memories of the captain) or killed by the Vex. Unable to contact help, the ship's AI, Failsafe, became dormant until she was awoken by the arrival of Cayde-6.

City Age
Approximately 126 years before the SIVA Crisis, Nessus re-entered the Solar System after an unexpected delay. The Arcadian Valley patrol space is scattered with the remains of the Exodus Black, picked clean by Fallen scavengers. At some point, the Vex, overseen by the Axis Mind Argos, Planetary Core, fully converted Nessus into a Machine World.

The Axis Minds of Nessus are noted to have higher than average computational power. One such mind imprisoned Failsafe for attempting to access the Vex Network. Sagira sought out another such Mind in order to analyze a map of the Infinite Forest.

Red War
Following the Red Legion's invasion of Earth, they began to mobilize their forces across Nessus in an attempt to uncover any secrets it harbored. During this mobilization they came into conflict with the local Vex population as well as the Fallen House of Dusk which was scavenging whatever they could from the remnants of the Exodus Black.

Following the death of Dominus Ghaul, Calus' flagship, The Leviathan, arrived at the Solar System and began to consume sections of the planetoid. . Doing so caused Argos to be sucked into the Leviathan's vacuum alongside a squadron of Vex, forcing Calus to call upon the Guardians to be rid of the Vex Mind for good. Succeeding in destroying the Axis Mind, the conversion of the planetoid has been permanently halted but the Leviathan continues to slowly consume Nessus into Royal Wine.

Post-Red War
When the Black Fleet arrived, Nessus was one of the few worlds in the outer system that was left untouched by the Pyramids. However, sometime after their departure, Calus and the Leviathan mysteriously disappeared from Nessus's orbit, leaving the Machine World only partially consumed.

Sometime afterword, Calus's daughter and current leader of the Cabal Empire, Caiatl, arrived at the Sol System with her legions. Nessus was the first world to be invaded, with an Imperial Land Tank being deployed in the Arcadian Valley. It was here where her forces and the Guardians first clashed against one another in a bid for dominance over the system.

Locations

 * Arcadian Valley
 * The Tangle
 * Well of Dust
 * Well of Echoes
 * Virgo Conduit
 * Chamber of Stone
 * The Mists
 * Vinculum Cell
 * Quiet Epiphany
 * The Fissure
 * Ancient's Haunt
 * The Cistern
 * Pools of Luminance
 * Well of Flame
 * The Anchor
 * The Conflux
 * Excavation Site VII
 * The Inverted Spire
 * Watcher's Grave
 * Chamber of Water
 * Artifact's Edge
 * The Orrery
 * Lost Fuselage
 * Hallows
 * The Tor
 * Sunken Cavern
 * Well of Giants
 * Exodus Black
 * Chamber of Sky
 * Prodromus Down
 * Well of Stars
 * The Rift
 * Glade of Echoes
 * The Carrion Pit
 * EX-077 Command
 * Endless Vale
 * Arcadian Strand
 * Distant Shore
 * Legion's Folly

Trivia

 * In an early development The Myriad was a working title for Nessus.
 * This makes sense, as Nessus could be described as a myriad in many manners. It contains mixtures of Fallen, Vex, and Cabal technologies, and is strongly influenced by all of those species. It is covered in mixtures of Fallen scavenges, Vex ruins and strange constructs, scattered bits of the Exodus Black, Cabal drills and structures, etc.
 * It is also one of a "myriad" of smaller barely-notable objects in the vicinity of the outer planets.
 * The Vex who reside on the planet bear slight technological and physical differences from those across the rest of the Solar System.
 * Large parts of Failsafe's ship, the Exodus Black, can be found along parts of Nessus. Scannables in the area indicate that Failsafe's crew tried to escape and survive, but died due to a lack of food and supplies.
 * Failsafe's crew do refer to the presence of the Vex, suggesting that the cyborgs were present when they arrived. Failsafe referred to the fact that she had been on Nessus long enough to see the Vex take over the entire planet, convert approximately 92% of it into a machine world like Mercury, and kill all life forms.
 * Armor and various lore pieces from Nessus have even suggested that the original crew of the Exodus Black was headed for Kepler 186f, a habitable planet very far from the Solar System. Some unknown force (possibly Vex technology) caused the ship to lose control and veer towards Nessus, which was near its path at the time. The engines and some parts of the ship malfunctioned, resulting in a crash landing. That was when the crew of the Exodus Black would face the Vex and meet their ends.
 * Some birds and small animals can be seen flying over and around areas on Nessus. Plant life also exists there. It is unknown whether Nessus actually held life before the arrival of the Vex. Neither Ghost nor the other Vanguard members suggest that the Traveler terraformed it, however, some scannables give evidence that the life on Nessus is artificial, being created by the Vex for unknown purposes.
 * Nessus could possibly be the farthest location the Guardians have traveled to in the Destiny series.
 * Nessus, owing to the scattered small groups of Vex found across its surface, usually consisting of either a small group of Harpies, Hobgoblin snipers entrenched atop pillars, or a Minotaur, 1-2 Hobgoblins wielding Laser Rifles and several Goblin "attendants", is a location that often involves guerrilla warfare by scout Guardians against the Vex occupying forces and the Vex units stationed on Nessus. Public events such as the Spire Integration usually involve more direct confrontations between Guardians and the Vex.  Owing to their slow movement and tendency to stay in the open, Vex units in the forests of Nessus often fall prey to snipers lurking in the trees, while guardians carrying swords can easily cut down a group of patrolling Vex in seconds.  Even Hydras can be easily killed in guerrilla assaults by guardian scouts or picked off by snipers.

List of appearances

 * Destiny
 * Age of Triumph
 * Destiny 2
 * Curse of Osiris
 * Warmind