The Mass Effect series tells a story which concerns the fate of the entire Milky Way Galaxy. The narrative that culminates within the original trilogy begins with events that are put in motion billions of years prior to Mass Effect 1. The Reapers, an ancient species of machines, bring about a galactic apocalypse every 50,000 years or so in a misguided attempt at preserving life through the harvesting of organic tissue. In 2183, the year Commander Shepard becomes the first human Spectre, the galactic community which occupies Citadel space and the rest of the Milky Way is blissfully unaware of the threat to its existence.
[Warning: Spoilers for the first three Mass Effect games below]
Those looking forward to playing Mass Effect for the first time after the Legendary Edition remasters release should be warned that spoilers for the entire trilogy will follow. Although events follow a set timeline, the exact nature of those events are subject to change based on player action throughout the course of a playthrough. However, as a dialogue-heavy RPG, Mass Effect is best experienced with no prior knowledge of how events might transpire according to player input.
The Reaper threat may be billions of years in the making, but the entire original Mass Effect trilogy takes place over the course of three years. As of now, it is unclear when the new Mass Effect game in development will take place on the timeline, but trailer hints point to a Mass Effect 3 follow-up before the Andromeda Initiative completes its journey.
Mass Effect Timeline - Major Events in the First Mass Effect
The first Mass Effect, which will be helped by Legendary Edition improvements the most, takes place 35 years after the discovery of Prothean ruins buried on Mars, and humanity has assimilated into galactic culture after a brief conflict known as The First Contact War against the Turians. Many see humans as ambitious and impatient due to their relatively short lifespans, but the Earth Systems Alliance has become an invaluable military and exploratory asset to the Citadel Council, the governmental body of the nine Citadel races.
Commander Shepard serves as Executive Officer under Captain Anderson aboard the SSV Normandy. In Mass Effect's prologue, Commander Shepard is dispatched alongside Humans Kaiden Alenko and Ashley Willams to a human colony on the planet Eden Prime - a specifically targeted locale for improved graphics in the Legendary Edition - in order to retrieve a Prothean beacon that was discovered. During the mission, Shepard is attacked by the Geth, a machine race created by the Quarians who were subsequently driven into a nomadic lifestyle aboard a starship fleet by their rebelling creation. The skirmishes on Eden Prime begin a wider conflict between Humans and the Geth called the Eden Prime War.
It is discovered that a rogue Spectre named Saren is commanding the Geth forces on Eden Prime for unknown reasons. Shepard locates the Prothean beacon, activates it, and is subjected to prophetic visions of synthetic beings slaughtering organics before falling unconscious. The Commander awakens on the Normandy, which is returning to the Citadel to inform the Council of what happened.
The Council is doubtful of Saren's betrayal and demand proof from Shepard that he has gone rogue. While investigating the matter, Shepard has the opportunity, based on player choices, to recruit squad members Garrus Vakarian, a Turian, and Krogan Urdnot Wrex. Evidence incriminating Saren in the Eden Prime attack is recovered from a Geth memory core by a Quarian named Tali'Zorah nar Rayya, who also joins Shepard and the Normandy crew. The memory core also reveals that Saren is looking for something called the Conduit, which will aid him in bringing about the return of the reapers.
When reporting to the Citadel Council, they find the evidence of Saren's actions on Eden Prime enough to strip him of Spectre status, but dismiss the Reaper doomsday implications as mere rumors. Shepard is then promoted into the ranks of the Spectres, the first Human to do so. The Spectres are elite agents which report to the Council directly, and have a tremendous amount of authority within Citadel space. Shepard is tasked with tracking down Saren.
While leaving the Citadel and Mass Effect's very long elevators, Anderson is relieved of his command and Shepard is given the Normandy. Anderson informs Shepard there have been reports of Geth activity on the planets Noveria and Feros. He also mentions that an ally of Saren, Asari Matriarch Benezia, has a daughter named Liara T'Soni who is an archeological expert on the Protheans.
The Normandy eventually finds Liara on the planet Therum investigating Prothean ruins, but has come under attack by the Geth. Once Liara has been rescued from the ruins, Shepard shares with her their vision from the Prothean beacon, and Liara offers her hypothesis that the Protheans were not the first interstellar civilization to suddenly become extinct.
With Liara (a potential romance option in Mass Effect) becoming a part of the crew, the Normandy goes to Noveria, the home of a company known as Binary Helix, which Saren and Benezia are investors in. When Shepard arrives, they learn that Benezia has recently come to Noveria on business, but the Binary Helix lab has started issuing a distress signal. The lab is found to be overrun by Rachni, a dangerous hive-mind species thought to be extinct. Binary Helix found a Rachni Queen egg and attempted to breed an army, but the Rachni turned on the scientists. Benezia is found with the Rachni Queen and attacks Shepard. After fighting with her, the indoctrination that Saren used to control Benezia is broken, and she tells Shepard that Saren was looking for the location of the Mu Relay in the genetic memory of the Rachni Queen.
The Mu Relay's location was lost after it was moved by a supernova, but ended up somewhere in Rachni controlled space before the Rachni Wars. Benezia is unaware of Saren's plans involving the Mu Relay, but gives Shepard the coordinates before succumbing to the indoctrination again, needing to be killed. Afterward, Shepard has the option to either free the Rachni Queen, which promises to raise its offspring peacefully, or once again cast the species into extinction.
The Normandy then travels to the planet Feros, where repeated Geth attacks have occurred. It is discovered that a local company called ExoGeni Corporation has been experimenting with an ancient plant creature, the Thorian. Colonists on Feros are being controlled telepathically by the Thorian, and after fighting colonists, humanoid creatures called Thorian Creepers, and Asari clones produced by the Thorian, Shepard manages to kill the hostile and ancient creature, a boss fight that may have more cover available in the Legendary Edition.
The original Asari that was being cloned then emerges from the Thorian and explains that she was offered to the plant as a sacrifice by Saren in exchange for the Cipher, the collective cultural consciousness of the Protheans and key to understanding the visions Shepard was given by the beacon. The Thorian was at least 50,000 years old, and observed the Protheans when they lived on Feros, consuming some to gain their knowledge. Saren's sacrificial Asari then gained the Cipher while inside the Thorian, and transfers it to Shepard through a mind meld.
While following these leads to find Liara and investigate the Geth activity on Noveria and Feros, the Council contacts Shepard with another lead: a Salarian espionage team has been investigating Saren's activities on the planet Virmire, and recently sent a distress signal. When the Normandy arrives, they find a lab being used by Saren to breed an army of Krogan immune to the Genophage. A plan to destroy the facility is formed, and Shepard is confronted by Wrex, who is furious that Shepard would throw away an opportunity to find the Genophage cure. Depending on dialogue, and Shepard's alignment in the Renegade and Paragon system, the player can either convince Wrex to remain a squad member, kill him, or allow Ashley to shoot him.
Inside the facility, Shepard discovers that its true purpose is to learn the mechanisms behind the Reapers' indoctrination technique, which Saren used on Matriarch Benezia. Another Prothean beacon is discovered, which provides Shepard with a second vision, and a hologram of Sovereign appears. Sovereign is the vanguard Reaper left in the Milky Way tasked with facilitating the Reaper invasion, and tells Shepard that the Citadel and Mass Relays were built by the Reapers - not the Protheans - to help usher organic life to its apex before the Reapers commence harvesting.
Leaving the indoctrination/breeding facility, Shepard arms a nuke but is assaulted by Geth forces led by Saren. Kaiden and Ashley are both pinned down, and only one can be saved from the nuclear explosion. Saren attempts to recruit Shepard to Sovereign's cause before escaping prior to the explosion. Shepard must make one of Mass Effect's biggest choices and select between saving Kaiden or Ashley, with one being killed in the facility's destruction.
Thanks to the second Prothean beacon and the Cipher, Shepard has a complete vision, and recognizes it as a distress call that was intended to warn the Protheans of the impending Reaper invasion 50,000 years ago. The origin of the message is a planet called Ilos, which is only reachable through the Mu Relay. However, the Citadel Council does not believe the Reaper threat exists and grounds the Normandy, intending to set up a blockade to defend against Saren's growing army. Captain Anderson helps Shepard steal the impounded Normandy, which uses its state-of-the-art stealth technology to escape and travel to Ilos in pursuit of Saren.
Finding a Geth fleet surrounding the planet, Shepard quickly follows Saren to the surface. They soon discover a Prothean Virtual Intelligence known as Vigil. Vigil informs Shepard that the Citadel is actually a cleverly designed trap, serving as a gigantic Mass Relay that connects to dark space outside of the Milky Way where the Reapers lie in wait. Sovereign's goal is to activate the Citadel, ushering in the next galactic genocide. The Protheans were unable to determine the ulterior motive behind the Reapers cycle of destruction.
Vigil informs Shepard that the Conduit was a miniature, experimental Mass Relay built by the Protheans linking Ilos to the Citadel. After the Prothean extinction, 12 scientists emerged from cryogenic hibernation on Ilos, and used the Conduit to travel to the Citadel and altered the signal the Reapers use to activate the Citadel's Relay to dark space. Saren's plan is revealed: he traveled through the Conduit to the Citadel and wants to undo the work of the Prothean scientists, allowing Sovereign to signal the other Reapers.
Shepard travels through the Conduit and begins fighting through the Citadel, eventually confronting Saren in the Council chambers. If Shepard can convince Saren that Sovereign's plans are wrong, Saren overcomes the indoctrination and shoots himself; if not, Shepard must kill Saren. With Saren out of the way, Shepard uploads Vigil's program to the Citadel and opens the closed arms of the Citadel, allowing the Alliance fleet waiting outside to enter and confront Sovereign. A synthetic husk forms from Saren's body, the final boss of Mass Effect. Shepard defeats the husk and the fleet destroys Sovereign, delaying the Reaper invasion.
Mass Effect Timeline - Major Events in Mass Effect 2
The beginning of the risk-taking game Mass Effect 2 opens with Commander Shepard's death. The Normandy is attacked by an unknown vessel, and the stealth tech is useless against it. Shepard saves the crew, sacrificing their self as the Normandy debris crashes into a nearby planet.
Two years later, in 2185, Shepard awakens aboard a Cerberus space station. He was brought back to life by Cerberus in order to truly face the threat of the Reapers outside of the Council's control. Shepard escapes the space station when it comes under attack and eventually is granted an audience with Cerberus' benefactor, the Illusive Man. The Illusive Man instructs Shepard to investigate missing Humans at a colony called Freedom's Progress. Shepard, along with Cerberus operatives Jacob Taylor and Miranda Lawson (both of which can be romanced), go to the colony and are confronted by an alien species called the Collectors. Tali, Shepard's former crew member, is encountered on Freedom's Progess and is surprised to see Shepard alive and working with Cerberus, which is notorious for its anti-alien sentiments.
Shepard and Tali part ways, and Shepard reports to the Illusive Man. Shepard is given command of the Normandy SR-2 - a larger ship based on the original - and is surprised to see Joker, the pilot, and Dr. Chakwas aboard, along with the ship's own artificial intelligence, EDI. Shepard is then tasked with forming a team to deal with the Collector threat, supplied with a dossier containing four leads: a Salarian scientist, a vigilante known as Archangel, a Krogan warlord, and a mentally unstable yet powerful biotic Human codenamed Subject Zero.
The Salarian scientist is found to be a man named Mordin Solus, and is on the asteroid-turned-space-station Omega trying to cure a plague engineered by the Collectors. Archangel is also found on Omega in a personal war against three different mercenary factions. Archangel's identity is revealed to be Garrus, who can be romanced in Mass Effect 2. The Krogan warlord is on a planet named Korlus, attempting to create a genetically perfect Krogan. When the warlord is killed, the lab-grown Krogan named Grunt is entrusted to Shepard. Subject Zero is acquired by Cerberus from her prison facility, but the warden turns on Shepard, hoping to capture the Commander for a reward. Subject Zero is eventually emancipated from the prison and reveals her real name to be Jack.
All four join the Normandy SR-2's crew, giving the player the opportunity to unlock bonus powers, and Shepard receives word that another Human colony is under attack from the Collectors on a planet called Horizon. Ashley or Kaiden, whichever survived Virmire in Mass Effect, is stationed on Horizon helping the colonists set up defense towers. When the Normandy arrives, the Collectors have already kidnapped many colonists and escape aboard a large ship. Similar to Tali, the Virmire survivor feels betrayed by Shepard's allegiance with Cerberus. It is also revealed that the Illusive Man suspected the Collectors were after Shepard, and sent an anonymous tip to the Alliance that the Commander was alive. The message was intercepted, leading to the Collectors attacking Horizon since a close associate of Shepard was there, confirming the Illusive Man's suspicions.
Three more team member dossiers are given to Shepard after Horizon, one of which is Tali. The other two are a Drell hitman named Thane Krios - who joins the Normandy crew hoping to find some purpose - and an Asari Justicar named Samara who joins Shepard after they help her with a murder investigation, or is betrayed in favor of recruiting Morinth. Tali is found on one of the Quarian home worlds occupied by the Geth. After she is rescued from a precarious situation, she too joins the Normandy crew.
Shortly after these party members are recruited, Shepard learns from the Illusive Man the Collector ship that escaped Horizon has been disabled, allowing for an opportunity to board it and investigate. Aboard the Collector ship, it is discovered that the Collectors are actually the remnants of the extinct Protheans, genetically modified beyond recognition to serve the Reapers. Shepard also comes to realize that the Collectors are researching their own genetic compatibility with Human DNA, and that millions of pods within the ship must be for capturing more Human subjects. While accessing the Collector ship's systems, EDI finds out that the ship is not disabled, but a trap to lure the Commander - which the Illusive Man was aware of.
After escaping the ship, Shepard confronts the Illusive Man, who claims the risk and ruse were necessary to get the information on the Collectors, which has led to a revelation regarding the Collector home world and the Omega-4 Relay. The Omega-4 Relay is the only way to reach the Collector home world, which lies near the galaxy's core. The Relay requires a Reaper IFF (Identification, Friend or Foe) to safely traverse, since the destination is near a black hole and requires very exact coordinates for survival.
A Reaper IFF has been located by Cerberus in a disable Reaper which was apparently destroyed millions of years ago in Mass Effect's history by a race that predated even the Protheans. The weapon that disabled the Reaper also left a mark on the planet Klendagon named Great Rift Valley. When aboard the Derelict Reaper, the crew of the Normandy discover that the power core is still intact, facilitating the indoctrination of any organisms that came on board, including Cerberus scientists. Shepard also encounters a single Geth soldier, which appears friendly and helps recover the IFF, being disabled in the process. If Shepard decides to reactivate the Geth (instead of giving it to Cerberus for research) it joins the crew with the moniker Legion being provided by EDI.
Shortly after, the Reaper IFF is found to contain a homing signal, intended as a trap by the Collectors to locate the Normandy. While Shepard is away on a mission, the Normandy is overrun by Collectors, requiring Joker and EDI to take back the ship. The Normandy, under the control of EDI, escapes the Collector ship, but not before every crew member except Joker is taken by the Collectors. It is here that the player makes the choice to either traverse the Omega-4 Relay in short order, or complete other ME2 missions first, possibly jeopardizing the lives of the taken Normandy crew members.
When the Normandy uses the Reaper IFF and comes through to the destination of the Omega-4 Relay near the galactic core, a massive Collector base is discovered. Fighting off a Collector ship, the Normandy crash-lands on the exterior of the base, with crew members possibly dying in the crash depending on how many upgrades the player made to the ship throughout the game. More casualties can occur during the following infiltration of the Collector base dependent on assignments given, squad member loyalties secured, and number of missions completed before going through the Omega-4 Relay.
Inside the base, Shepard encounters the Collector General, which is being directly controlled by Harbinger, the original Reaper and mastermind behind the Collectors. Once Shepard reaches the heart of the Collector base, a Reaper in the shape of a Human is found in the early stages of construction. Shepard has the option to either destroy the Collector base, or use a radiation pulse to annihilate all the Collectors on board and preserve the base for Cerberus' research. Regardless of the decision, the Human Reaper awakens and attacks Shepard after the destruction plan has been set in motion. After destroying the Human Reaper, Shepard escapes with potentially everyone still alive on the Normandy, and Mass Effect 2 ends in a cutscene showing the Reapers activating in dark space and beginning their invasion of the galaxy.
Mass Effect Timeline - Major Events in Mass Effect 3
Mass Effect 3 begins with Shepard's voluntary return to the Earth Systems Alliance and the invasion of Earth by the Reapers. Shepard, Anderson (now an Admiral), and a man named James Vega escape the Reapers' destruction of the Alliance building in Vancouver and are rescued by Ashley or Kaiden (whichever survived Virmire) aboard the Normandy, with Anderson electing to stay on Earth to lead the resistance.
Shortly after, Shepard is told of a lead on Mars by Admiral Hackett. Liara has uncovered blueprints in the Prothean ruins on Mars for a device that might turn the tide against the Reapers; however, Cerberus was encountered on the red planet and have also found that information. When accessing the Prothean beacon in the archives on Mars, the Illusive Man appears as a hologram and informs Shepard of his plans to find a way to control the Reapers in order to evolutionarily elevate humanity above the other races of the galaxy. Shepard escapes from Mars with the Prothean information just before Reaper forces arrive, though the Virmire survivor is critically wounded in the process.
After arriving on the Citadel in Mass Effect 3, the Council does not believe in the Prothean device's ability to stop the Reapers, since it failed to protect the Protheans. Liara tries to explain that the Protheans were missing a component known as the Catalyst, but the Council says the galaxy is preparing for a more conventional war effort and organizing a summit to make a strategy. Shepard's Spectre status is reinstated, and he is recruited to unite the galaxy, starting with the Turians, although there is no set play order to many of ME3's missions.
Shepard travels to the Turian home world of Palaven, landing on its moon, Menae, and learns that the Turian Primarch has been killed. If Garrus survived the final mission in Mass Effect 2, he is reunited with Shepard on Menae. Garrus is once again a romance option in Mass Effect 3, and joins them and Vega on a mission to reestablish communications with the new Primarch, who agrees to join the summit and tells Shepard they will need to recruit the Krogan. Upon leaving Menae, Shepard finds EDI has implanted herself in a synthetic body allowing her to join Shepard on missions outside of the Normandy. Shepard also receives word from Admiral Hackett that the Alliance has begun construction on the Prothean weapon under the codename Project Crucible.
When trying to recruit the Krogan for help in the war against the Reapers, Shepard is assured their help if a cure for the Genophage can be found. The Krogan leader - Wrex if he survived in Mass Effect, or his brother Wreav if not - informs Shepard that there is an experimental lab that has produced fertile Krogan females who are immune to the Genophage, and that a cure can be synthesized there and dispersed on Tuchanka, the Krogan home world. When the Normandy arrives at the lab on Sur'Kesh, only one female Krogan has survived after the cure left them with a weakened immune system. She is under the care of Mordin Solus if he survived in Mass Effect 2.
The team extracts the Krogan female after an attack by Cerberus, which hopes to stop the development of a Genophage cure. When Shepard goes to Tuchanka with the cure in hand intent on dispersing it into the atmosphere, they are offered assistance in completing the Crucible by the Salarian leadership in exchange for not administering the cure and dooming the Star Trek-inspired Krogan. It is then found out that using the tower which spread the Genophage to now spread the cure is a suicide mission, and Mordin (or his replacement, Padok Wiks) offers to sacrifice themselves in order to spread the cure. The player can choose to let them go ahead with the cure, try to talk them out of it, or kill the Salarian if persuasion fails.
Following the dispersal or destruction of the cure, Shepard receives a request from the Salarian Council member to have a meeting regarding the suspicious activity of the Human councilor Udina. Shepard arrives to find the Citadel under attack by Cerberus, an attempted coup orchestrated by Udina. In the course of the coup attempt being resolved, Shepard may have to kill the Virmire survivor (who has recovered from their injuries sustained on Mars), and Udina ends up dead.
Shepard leaves the Citadel and hears that the Turian and Krogan forces on Palaven need reinforcements, and that the Quarians may be persuaded to help. The Quarians are in the midst of retaking their home world from the Geth, but were stonewalled when a signal from the Reapers increased Geth combat capabilities. Shepard, alongside Tali or one of the Quarian Admirals if Tali died in Mass Effect 2, manages to get inside the Geth dreadnought broadcasting the Reaper signal and extract the Geth unit responsible - Legion if it survived in Mass Effect 2, or a Geth VI in Legion's likeness. The dreadnought is then destroyed and Shepard learns that the Reaper signal must be destroyed at its source on the planet Rannoch.
The signal base turns out to be a Reaper itself and, after being bombarded, converses with Shepard, explaining the harvest cycle must be allowed to continue in order to preserve organic life from destruction via chaos. After the Reaper dies, the Geth fleet is left disabled and Commander Shepard has a choice to make: allow the Geth to gain true intelligence and destroy the Quarian Migrant Fleet, delay the evolution of the Geth and give the Quarians time to eradicate the Geth, or - if possible based on a number of previous player actions - broker peace between the two. Whichever fleet survives (or both) will aid in the war against the Reapers alongside forces assembled through Mass Effect 3's multiplayer.
The Normandy crew is then enlisted by the Asari councilor to retrieve a Prothean artifact that may help identify the Catalyst from the Asari home world, Thessia, which is under siege from the Reapers. Shepard discovers the artifact to be a Prothean beacon, which activates upon Shepard's arrival thanks to the Cipher. A Prothean VI, Vendetta emerges and explains the Crucible is not only a Prothean contraption, but a collaborative effort spanning millions of years and many Reaper cycles. The conversation is interrupted by Vendetta detecting an indoctrinated presence, which turns out to be an agent of Cerberus. After another conversation with the Illusive Man, and a fight against Cerberus operatives, Cerberus escapes with the Prothean VI and more Reapers arrive to destroy Thessia.
Following a lead on Cerberus to Sanctuary, a refugee camp for survivors from the Horizon colony, Shepard discovers a facility conducting research on indoctrination and learns Cerberus plans on attempting to control the Reapers. The lab is run by Henry Lawson, Miranda's father, who is killed one way or another at the end of the mission. Alerting Admiral Hackett to the discoveries on Sanctuary, an Alliance fleet is dispatched to address the threat of Cerberus. Once the VI is located, it is revealed that the Catalyst is in the Citadel itself, a design choice made to boost the power of the Crucible and integrate it into the Mass Relay network. Unfortunately, the Citadel has been reclaimed by the Reapers, who have moved the space station into orbit around Earth.
A plan emerges for Mass Effect 3's final battle on Earth involving all the factions Shepard managed to recruit throughout the three games. Ground forces will attempt to take London, where the Reapers have set up a teleportation beam between the planet's surface and the Citadel. Meanwhile, a fleet will remain outside of the Sol System, ready to bring in the Crucible when the ground forces take the Citadel and open the station's arms. During the ground assault, many Reapers, including Harbinger, abandon the space battle to protect the teleportation beam. Shepard is critically wounded by Harbinger, and the Reaper returns to the battle above thinking itself victorious.
Shepard manages to stumble into the beam, and is teleported into a tunnel on board the Citadel, followed by Anderson, who winds up in a different tunnel. The two meet but are soon ambushed by the Illusive Man, signs of Reaper indoctrination apparent all over his body. After dispatching the indoctrinated Illusive Man, Shepard and Anderson (if Anderson survived the fight) open the Citadel's arms and instruct the Alliance fleet to dock the Crucible. However, nothing happens. Anderson and Shepard have one final conversation before Anderson succumbs to his wounds. Shepard falls unconscious shortly after.
When Shepard awakens, they have been teleported to a different part of the Citadel and are confronted by the Catalyst, which takes the form of a boy Shepard saw killed on Earth during the Reaper invasion. The Catalyst reveals that it is actually the Intelligence, the AI created by the Leviathans and inventor of the Reapers. The Intelligence explains its cycle of annihilation to Shepard, but notes that the successful completion of the Crucible means the cycle will no longer be viable for preserving life.
Shepard is faced with three options to decide the fate of the galaxy. The Crucible can be used to destroy the Reapers and all synthetic life in the galaxy, control the Reapers by usurping the Intelligence with Shepard's consciousness as the new AI manipulator, or combining all organic and synthetic life and bringing about an end to inevitability of destruction via technological singularity. Shepard can also choose to deny making a decision with such great galactic ramifications and the Reapers will succeed in their harvest.
Shepard eventually makes a decision, an appropriately colored beam is launched from the Crucible, and the galaxy is changed forever in Mass Effect 3's controversial ending. The ultimate fate of Shepard, their crew, and the various factions throughout the galaxy can differ greatly based on the player's actions throughout the Mass Effect trilogy.