The Alien Machine or the Alien City is the conduit of the Codex created by the unidentified race of aliens who inhabited Tau Volantis. Located beneath a huge mountain overlooking the abandoned Sovereign Colonies' research base, the city-esque machine housed the corpses of the deceased species and their Necromorph counterparts.
The massive structure of the Machine is a maze of paths and catacombs surrounded by pillars that led to the control center for the Codex. The bodies of the aliens themselves appeared to be one with the Machine, standing erect or hunched over the pathways leading to the conduit, their arms and legs seemingly fused with the stone like structures that they are pressed against.
Special platforms that amplified the use of kinesis and stasis are scattered throughout the Machine and are particularly situated before doors that required the decryption of the modified language used by the aliens to bar or allow entrance to certain areas. The "promenade" in particular is an area surrounded by an arch; situated before large doors and monoliths that required the manipulation to successfully activate the kinesis boost that will launch the traveler across great distances in a short amount of time. Opening all pathways allowed easier access to the Machine.
Eroded by the passage of time, when the city is rediscovered by the Sovereign Colonies in 2311, it's pathways are obstructed by thick and sticky webbing. The possible remains of the Corruption are created by the Necromorph life form. Years later, in 2514, remnants of the deep dig team's work, scaffolding, construction material and generators still remained scattered throughout the massive structure which is a sign of their incomplete work.
After the Convergence Event that wiped out the aliens, the Machine was hidden underneath a huge mountain. The Sovereign Colonies set up a huge base right at the base of the mountain as well as on top of the mountain peak. A huge wall was set up around the perimeter. A lift system was built on the mountain side to allow travel between the mountain top and the colony below as well as an underground "tram" system to allow an easy and quick travel of men and supplies. However, as the cleanse order was executed, the base was abandoned with the lifts and tram system cut off until 2514.
Events of 2314 and 2514
In a move to prevent the completion of the Convergence Event triggered by the Markers, the aliens constructed the Machine and a Codex that would freeze the planet and pull the Moon down onto Tau Volantis killing it. For whatever reason (Presumably Necromorphs), they never completed the Machine so they created a language that could be utilized by future species in the event of discovery, warning them of the danger and how to complete the Machine when it is found.
Two million years later, in 2311, the Sovereign Colonies Armed Forces discovered the planet by triangulating the signal perpetuated by their own Markers. Research teams led by Dr. Earl Serrano found their way into the underground of the frozen and seemingly barren planet. There, they found the frozen corpses of the aliens within their city. In awe at their sheer size and majesty, the researchers then explored the city and discovered a wealth of artifacts. Little by little, the more Markers and lifeforms that they unearthed, the closer to the truth they became.
Eventually, Earl Serrano figured out what happened on the planet and tried to finish what the aliens started when they halted Convergence. Unfortunately, the spread of the Necromorph life form, using the bodies of their fallen soldiers and researchers complicated the situation. His efforts were largely thwarted by General Spencer Mahad and the "Scenario Five" order which entailed the eradication of all personnel and the destruction of all information on the aliens including the Codex. The planet and the Sovereign Colonies expedition remained lost to history for the next two hundred years before the accidental rediscovery of old SCAF information in 2514 by Marker researcher Damara Carver on Uxor.
Ellie Langford, a friend of Damara sought to complete the doctor's work and with the help of Robert Norton and Damara's husband, John initiated the journey to the planet to stop the spread of the Necromorphs. When Isaac Clarke is brought out of hiding, Langford's efforts to reach the planet are largely successful through his understanding of Marker script, thinking that Tau Volantis is the Marker Home world. Hounded by the Unitologists led by Jacob Danik who wanted to stop them, they raced to piece together the broken information left behind by Serrano. They learned what the late scientist did two hundred years ago and from there, they rebuilt a Codex from the memories of Rosetta.
Though Isaac and Carver ventured into the heart of the Machine to stop Danik from restarting the Convergence Event, the Unitologist used the Codex to free the Moon from hibernation which triggered Convergence, the Moon proceeded to tear apart the Machine and the mountain. Battling the massive Necromorph, Isaac and Carver eventually managed to disable the creature long enough to reactivate the Machine with the Codex and destroy the Moon. Their efforts resulted in the halting of the Moon's signal altogether.
- The Machine may be a massive structure which is powered with the use of a similar force as the stasis and kinesis, as seen by the pedestial, which supercharge the kinesis and stasis units of Isaac and Carver. With the use of these elements, the Machine is able to pull something as large as the Moon out of the orbit down onto the planet, however, it is unknown how and if the stasis capability contributed to the freezing of the planet, as the stasis technology used by humans seems to alter the passage of time in its area of effect, and does not actually freeze the target into a block of ice.