Tau Volantis was the home of an unidentified race of aliens. Long ago it was a planet of water, its inhabitants appearing semi-aquatic in nature. Not dissimilar to the inhabitants of Earth, the aliens discovered a Marker and soon thereafter began to create copies of the Marker in move to harvest its energy. They worshiped the Marker and fell under its thrall. The combined power of Markers and the inhabitants who've fallen victim to its control triggers a Convergence Event.
However, what few may have resisted the call of the Marker created a Codex which would work in conjunction with a terraforming machine. Their efforts are only half successful: the halt of the Convergence Event deep freezes the planet into a frozen wasteland, leaving the final life cycle of the Necromorph life form, a sentient moon, incomplete and semi-dormant.
Two million years later, a faction known as the Sovereign Colonies discover the signal being perpetuated by their own Markers comes from the lost planet itself. In the face of losing the Secession War to Earth Government[note 1], the colonies send an expedition out to the planet in the hopes of finding Markers for their flagging campaign. Now an "icy backwater planet", the environment of Tau Volantis is harsh, and visited frequently by snow storms. These conditions complicate vehicular or on-foot travel for research teams and soldiers; the combination of strong winds, freezing temperatures and thigh-high snow often stalling travel altogether. When the expedition unearths the corpses of the aliens changed by the Necromorph organism, it isn't long before that expedition itself succumbs to the influence of the Markers.
When General Mahad loses complete control of the situation, the Sovereign Colonies council authorizes Scenario Five; a "first contact" scenario that entails the death of all parties involved with the expedition in a move to prevent hostiles from reaching the Earth. In an effort to save the information discovered on the alien's machine and Rosetta, Earl Serrano and his search team halve the bones into pieces to hide. Serrano's attempts to prevent the restart of the Convergence Event himself are prevented by Mahad and an accident leaves him unable to walk. The expedition is lost. Two hundred years pass; the derelict Sovereign Colonies Armed Forces flotilla float above the planet in ruins, its crew lost to the ravages of the planet and their fellow man under orders from their government.
Outposts, industrial areas, research facilities and way stations scattered throughout the frozen environment are mere remnants of what was an established settlement on the planet. The frozen Tau Volantis' terrain appears to be made up of catacombs, sweeping cliffs and caves. Research founded by Serrano suggests that the terrain of the planet have been the home of marine life.
Langford's efforts to reach the planet urges Captain Norton and Sergeant John Carver to enlist Ishimura survivor, Isaac Clarke's help under the advisement of Langford. Above the planet they assume Tau Volantis is "Marker Homeworld", the origin of the Necromorphs. On the planet however, further exploration into the Sovereign Colonies fragmented data reveals Tau Volantis once was the center of a "Marker Uprising" that was subsequently halted before it could progress any further some two hundred years ago. For that reason, militarized followers of the Church led by Jacob Danik aim to stop Clarke and Langford from reaching the source and destroy all changes of true Convergence.
The planet is overrun by Necromorph lifeforms, all who appear to have adopted new ways of attacking unsuspecting victims with the use their own weapons and deceiving appearances. Wasters and Feeders are some of the hostile lifeforms encountered by survivors on the planet. The nature of the Necromorphs formed with human bodies are largely same in behavior and appearances as the ones previously engaged on Aegis VII, the Ishimura and Titan Station.
Further down below, however, creatures akin to the Snow Beast, and the Nexus emerge, revealing the fate of the planet's original inhabitants were the perpetrators of the "uprising" that halted the Convergence Event that required the sacrifice of their lives to stop. Though Danik is initially successful in restarting the Convergence Event, the combined efforts of Clarke and Carver result in the death of the sentient moon and the complete halt of the Marker signal.
Following the death of the Moon, Clarke and Carver eventually wake up to discover they have survived their freefall onto the planet's surface. At this point the moon, although dead and no longer broadcasting its signal, rests atop the planet's surface, remaining largely intact. The destruction of the machine seems to have no effect on the planet's weather and despite the death of the Moon, the necromorphs inhabiting the planet still exist, likely fueled by the long-range signals of the newly-awakend Brethern Moons.
Long before the Marker landed on the planet, Tau Volantis was presumably an aquatic planet with vast oceans covering the surface. Aside from the carvernous caverns and "cities" erected by the planet's former inhabitants, fathomless gorges and trenches runs along the ocean bed which now serves as tall cliffs and mountains. Once the Aliens activated their Machine, the whole planet was flash-frozen, plunging it into an endless snowstorm and apparently rendering the natives extinct.
Although no other species aside from the indigenous Aliens have been confirmed as natives to the planet, The Snow Beast is presumed to be a local creature, though its status as a Necromorph/natural being remains unclear.
An odd point about Tau Volantis is that its atmosphere is completely breathable to humans despite its complete lack of trees and natural oxygen factories, though the Sovereign Colonies's scientists might have probably terraformed the planet somehow to provide air, or that its natural ecosystem contains oxygen within travelling air.
"Tau" (ταῦ) is the nineteenth letter of the Greek alphabet and symbolizes life and resurrection. "Volantis" is a genitive term, derived from "volans", meaning "fly" or "move swiftly". Together, "Tau Volantis" could mean "swift resurrection", a reference to the nature of the Necromorphs. The name might also be a play on "Atlantis", referencing the mythical aquatic city in reference to Tau Volantis formally being an aquatic planet.
↑Isaac: I've seen a lot of ships but never anything like these. Norton: That's because the Sovereign Colonies were sore losers. When they lost the Secession War to EarthGov, they scuttled their entire fleet. I'm surprised any survived. Rosen: What were they doing this far from home anyway? Isaac: If this is where Ellie went, you can bet it had something to do with the Markers. ---Chapter 3: The Roanoke