Centuries ago, Exodus Black inadvertently crash-landed on Nessus in the Arcadian Valley. Although Nessus was supposed to be nothing more than a wayward icy rock, it was somehow able to support life, and had even given rise to its own biosphere. While some of the crew and colonists survived the crash and made an effort to send distress signals to Earth, they perished when the Vex, who had already transformed most of the planetoid into another of their machine worlds, took notice. Failsafe, Exodus Black's emergency AI, became the sole remaining survivor of the ship.
During the Red War, the Cabal Red Legion established a presence on Nessus to research Vex technology. Likewise, the Fallen House of Dusk soon arrived to scavenge what tech they could, coming into conflict with both the Vex and the Cabal.
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