In the history of the Mass Effect universe, the Eden Prime War refers to the events of the first Mass Effect game. In 2183, the Human Alliance colony of Eden Prime was invaded by the Geth, a race of artificially intelligent machines created by the Quarians three centuries earlier. The Geth were known for being isolationists, avoiding contact with organics and destroying any vessels that ventured into their territory, but had never actively attacked inhabited planets. All that seemed to have changed when an army of Geth invaded Eden Prime for unclear purposes, later discovered by Alliance personnel to be in search of an ancient Prothean relic. Most disturbing of all was that they appeared to have been following the lead of one of the Citadel Council's top Spectre agents, Saren Arterius.

Investigations pursued by the crew of the SSV Normandy confirmed that Saren and the Geth were in search of something called "The Conduit", which would allow them to summon forth an ancient race of machines called "Reapers" that dwelled in the dark space past the Milky Way's boundaries. Apparently, the Geth worshipped these Reapers as some form of deities, viewing them as the pinnacle of synthetic evolution that would bring about the destruction of all organics in the galaxy. While Saren's status as a Spectre was revoked after his rogue status was confirmed, the Citadel Council would pursue no further action against him and dismissed all claims of the Reapers' existence. It was left up to the Council's newly-appointed Human Spectre agent Commander Shepard to investigate the Geth's activities and bring Saren to justice.

Events and BattlefrontsEdit

Eden PrimeEdit

Eden Prime was a prosperous Human settlement established on the border of the Terminus Systems. The planet's environment and gravity was similar to Earth and the colony was mainly comprised of farmland and archeological sites where Prothean ruins had been discovered. Saren Arterius and the Geth attacked Eden Prime in order to acquire a Prothean beacon that had been dug up and intended to use it to find the Conduit. During the attack, Saren's flagship Sovereign - which would later be discovered to be a Reaper - landed on the planet's surface, a feat that most spacefaring vessels of such size would be unable to accomplish. Survivors of the attack would recall hearing disturbing, sinister sounds emanating from the ship's engines, unaware that the sounds were in fact a result of the indoctrination effect generated by all Reapers. Prolonged exposure would have led to the colonists becoming enthralled to Sovereign's will, turning into mindless slaves.

During the Eden Prime attack, the Geth planted several explosive charges around the colony's tram station to stop Alliance personnel from following them to the dig site where the Prothean beacon was located. The charges were disabled by officers from the SSV Normandy, which had responded to the SOS sent out from the colony. Commander Shepard discovered the Prothean beacon before the Geth could secure it. Shepard touched the beacon, which showed the commander a confusing, garbled vision of enormous machines descending from the skies and laying waste to all before them: the extinction of the Prothean race. After the Prothean data had been burned into the commander's mind, the beacon exploded, depriving Saren of his prize.

The Geth landing parties were soon eliminated completely and the colony, while heavily damaged, survived. During the incident, Normandy officer Jenkins was killed by Geth scouts and the Turian Spectre agent Nihlus was killed by Saren himself.


After being granted Spectre status for exposing Saren and being ordered to find him, Shepard was granted command of the SSV Normandy by its former captain, David Anderson. The Normandy then began its mission of hunting down Saren and visited several planets where the Geth had been sighted. On the planet Therum, at the site of an ancient Prothean ruin, Shepard rescued and recruited Asari archeologist Dr. Liara T'Soni. T'Soni was an expert on Prothean artifacts and aided Shepard in deciphering the the message left in the Prothean beacon on Eden Prime. While Dr. T'Soni was saved, the Geth destroyed the ruins that she had been studying.


Shepard arrives at the planet Noveria and discovers that Matriarch Benezia - Liara's mother and a supporter of Saren's - has recently arrived. She and Saren are investors in Binary Helix, a bio-engineering firm, which has a lab up on Peak 15. Benezia has gone there on business. However the lab has since issued a Code Omega signal, meaning there are critical problems, and a blizzard has cut off shuttle access. After wrangling with the colony's administrator, Shepard manages to get a garage pass and drives up to Peak 15.

The facility is deserted save for Geth and bizarre insectoid creatures—the rachni—which have escaped from the labs. Shepard reactivates the station's VI, Mira, and goes up to Rift Station looking for Benezia. Rift Station is full of science staff sheltering from the rachni attack; Shepard can help them out but gets attacked by those loyal to Benezia. The squad finds out Binary Helix discovered a rachni egg that turned out to be a queen, and were trying to breed an army from her brood until the rachni turned on them.

Down in the labs through the maintenance area, Shepard finds Benezia with the Rachni Queen. The matriarch attacks the squad, but after a fierce battle Benezia manages to overcome the indoctrination that Saren has used to control her, and tells Shepard the truth. Saren wants the location of the lost Mu Relay, and sent her to retrieve it from the queen's genetic memory. Benezia doesn't know what else he is planning. She hands the coordinates over to Shepard, but becomes lost to the indoctrination again and the commander has to kill her. After deciding what to do with the Rachni Queen, Shepard leaves Noveria with Benezia's data and another piece of the puzzle.


Zhu's Hope - a Human colony founded on Feros by ExoGeni Corporation - suffered numerous Geth attacks as Saren attempted to find the Thorian: a sentient plant creature capable of controlling the minds of others. The Thorian had survived underground beneath the ruins of an ancient Prothean city and had lived during the Protheans' occupation of the planet. It had gained knowledge of the Prothean culture through centuries of study and by consuming the dead, thereby gaining something referred to as the "Cipher" which allowed it to comprehend information in the same way Protheans could. Saren had sought the Cipher in order to decipher the messages he had recieved from a Prothean beacon on Virmire and sacrificed one of his Asari agents to the creature in order to gain it. Commander Shepard would also gain the Cipher from the Asari - Shiala - as she had decided to turn her back on Saren and his plans after he sacrificed her.


The planet Virmire was Saren's main base of operations. He had established a laboratory complex on the planet and was using it to breed an army of Krogan clones as well as to study the affects of Reaper indoctrination on organic minds. Geth platoons were stationed all over the base and Armatures patrolled the area around the base several miles out. Shepard and the Normandy crew were forced to land outside the base perimeter beyond the range of the anti-air defences, using the Mako tank to battle their way through the Geth patrols. Aided by the Salarian Union's Special Tasks Group, Shepard was able to storm Saren's base and put a stop to his research. Within the inner sanctum of the base, Shepard also discovered Saren's Prothean beacon and even communicated directly with Sovereign, discovering then that Saren's ship was itself a Reaper. Shepard and co. learned of the Reapers' cycle of genocide against organic cultures and realised that the next Reaper invasion was imminent.

Shepard's team, with the aid of the Salarian STG unit, managed to plant a bomb that would destroy Saren's base. Some of Shepard's crew are pinned down by Geth forces and are unable to recieve rescue before the nuke explodes. While the mission is not without sacrifice, it is successful and Saren's base is destroyed.


Ilos is the site of an ancient Prothean colony and research facility. It is also the location of the Conduit, a Prothean-built mass relay that functions as a "back door" to the Citadel space station, the centre of galactic civilization. Saren and the Geth enter the facility and seal it behind them, using the Conduit to bypass the Citadel's security and disable the station from within. Many Geth remain on Ilos to stop Shepard from entering the facility, but Shepard uses the Cipher to interpret several Prothean consoles containing access codes and messages regarding the Protheans' own struggle against the Reapers.

When Shepard and crew enter the Prothean facility, they discover a VI known as Vigil, which acts as caretaker of the facility. Vigil explains the downfall of the Prothean Empire to Shepard and the true purpose of the Citadel: the station is a trap, an enormous mass relay linking to dark space, the starless space that the Reapers inhabit. The Protheans long ago used the Conduit to secretly board the Citadel in order to disable the signal used to command the station's Keepers to activate the Citadel relay, thereby allowing the races of the next cycle a chance to survive the next Reaper assault. Vigil offers a data file to Shepard that will grant the commander temporary control of the Citadel to stop Sovereign. Shepard's squad takes the file and drives the Mako past the Geth barricades defending the Conduit. The Mako hurtles through the Conduit and crashes into the Citadel's Presidium.

The Battle of the CitadelEdit

When Shepard's squad arrives on the Citadel via the Conduit, the station is already under attack by Sovereign and a fleet of Geth warships. The Citadel and Systems Alliance fleets throw everything they have at the invaders, but suffer significant losses. As the fleet attempts to stop Sovereign on the outside, Shepard's squad battles against the Geth forces inside. The squad reach Saren in the Presidium Tower, who is ready to activate the Citadel relay and allow the Reapers to invade. Shepard attempts to reason with Saren who has been indoctrinated by Sovereign the whole time, but a firefight ensues between Shepard and Saren that ends with Saren being killed. Shepard then uses Vigil's program to shut down the Citadel relay.

Shepard's squad check Saren's body to ensure that he's really dead, but suddenly the body re-awakens in a burst of energy that burns away Saren's flesh, revealing a nightmarish skeletal machine made from Saren's cybernetic implants. Saren's remains are possessed by Sovereign, who uses the cybernetic husk to attack Shepard. The battle is long and fierce, but Saren's husk is destroyed and the feedback causes Sovereign's defences to fail. With the Reaper disabled, the Normandy and all the surviving Citadel/Alliance ships open fire on Sovereign, destroying it.

Following the destruction of Sovereign, the remaining Geth forces retreat and Commander Shepard and the Normandy crew are commended for their bravery. In the weeks following the Battle of the Citadel, the Normandy is assigned to patrol the Terminus Systems to hunt down the remaining Geth forces that were loyal to Sovereign. During this period, the Normandy was attacked and destroyed by the Collectors and Commander Shepard was presumed dead. In the two years following the Normandy's destruction, the Alliance would continue the clean-up and eliminate virtually all remaining Geth in Council space.

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