The Mass Effect series is known for a rich history and the complex galactic culture it depicts. Over the course of three long RPGs in the original Mass Effect trilogy, hundreds of Codex entries are compiled for the player's benefit which provide insight into general knowledge concerning all facets of galactic life in the Milky Way, including the long history of the pre-human galactic community. Throughout the original first three Mass Effect games, Commander Shepard also makes many important discoveries that shed light on the pre-recorded history of the Milky Way.
Mass Effect: Andromeda also began the series' expansion into a second galaxy. Only one game so far has dealt with events pertaining to the Andromeda Galaxy, and a relatively low budget for Andromeda, combined with little in-game access to Andromeda history, leaves its Codex lacking in comparison. The entire timeline of events for the Mass Effect series is rather impressive, beginning far before recorded history, and extending into the futures of both Mass Effect 3 and Andromeda.
The discoveries of N7-turned-Spectre Commander Shepard on their journey to thwart the Reapers' extermination of all life in the Milky Way concerns events that happened before any intelligent life present in the games had even begun to evolve. The only exceptions to this are the Leviathans and Reapers, who are the progenitors and executors of the doomsday events within the games. Because of the ancient creation of the Reapers, the entirety of the Mass Effect timeline spans billions of years. The exact timeframes are unknown, since the cyclical annihilation of all sentient beings in the galaxy was so effective that very few pre-modern records of the Reapers remain.
Mass Effect Timeline - The Creation of the Reapers
Events concerning the story of Mass Effect begin at an unknown time potentially billions of years Before the Common Era (BCE), when a race of massive, highly intelligent exo-aquatic beings known as the Leviathans dominate the Milky Way Galaxy. The Leviathans rule over every other alien race they find, demanding tribute in return for protection. Over time, the Leviathans see a pattern emerging in which the intelligent life they rule over create a likewise subservient race of synthetic beings, which without fail revolt violently against their creators.
In an attempt to preserve all organic life, the Leviathans pull the ultimate sci-fi blunder in creating an artificial intelligence known simply as The Intelligence. The Intelligence in Mass Effect's universe is mandated by the Leviathans to preserve the existence of life in the Milky Way at all cost. To do this, The Intelligence creates pawns of unknown form to collect organic material for preservation throughout the galaxy. The Intelligence ultimately came to the conclusion that intelligent races created subservient synthetics in order to improve their own existence. However, the synthetics always sought to surpass their creators as an independent species, resulting in a technological singularity that annihilated the organic creators.
To rectify this problem, The Intelligence sought a means of destroying and harvesting sentient races before they were allowed to bring about their own destruction through a singularity, which would nullify any attempt at the mandated preservation. The solution was Mass Effect's Reapers. The Intelligence turned its pawns on its creators, harvesting the Leviathans in order to create the first Reaper, Harbinger, in their image. The memories of the harvested Leviathans combined to create the hive-mind consciousness of the Reapers, and also assimilated into the mind of The Intelligence.
The Intelligence harvested all other organic races in the galaxy, preserving their genetic material and using it to create more reapers resembling Harbinger. Thus began the cycle of organic species evolving throughout the galaxy, and being systematically eliminated by the Reapers for preservation in order to make room for more primitive species to evolve.
In an attempt to increase the efficiency at which this process occurred, The Intelligence had the Reapers create Mass Effect's Mass Relays and the Citadel, which allowed burgeoning species to travel easily throughout the galaxy, facilitating faster advancement toward their own annihilation and allowing for more frequent harvests by the Reapers. The Intelligence lay dormant within the Citadel, and a vanguard Reaper was left in the Milky Way to hibernate until the next harvest, while the remaining Reaper fleet lied in wait in dark space beyond the edge of the galaxy.
Mass Effect Timeline - The Protheans & Other Spacefaring Races
Many spacefaring races evolve in the Milky Way only to ultimately be eradicated by the Reapers. A handful of clues are left scattered throughout the galaxy, pointing to the impending doom awaiting the modern galactic races. Circa 37,000,000 BCE, an unknown alien race manages to kill a Reaper by firing a mass accelerator at it. The projectile, after passing through its target, impacts the planet Klendagon, leaving an unnatural geological feature that becomes known as Great Rift Valley. The discovery of this weapon and valley was made by Cerberus in the timeframe of Mass Effect 2, and the Derelict Reaper, which the ancient alien race destroyed, will eventually be investigated by Commander Shepard in one of ME2's most important missions.
Roughly 68,000 years before the Citadel Council is formed, a race known as the Protheans achieve spaceflight and proceed to colonize the galaxy by utilizing the Mass Relays - with the Citadel as the capital for what eventually becomes The Prothean Empire. The Empire was formed to address the threat of a hostile machine race, a conflict that would later be called the Metacon War.
Nearly 20,000 years later, circa 48,000 BCE, the Reapers arrive through the Citadel, which is actually a dormant Mass Relay designed as a trap to more efficiently exterminate the species that inhabit it, since any galactic civilization in Mass Effect's timeline will no doubt recognize its value as a space station. The war between the Protheans and the Reapers lasts centuries, with the Protheans making significant progress on a weapon to destroy the Reapers known as the Crucible. The Crucible was never finished, however, and the Protheans were eventually rendered extinct by the Reapers.
Mass Effect Timeline - The Pre-Council Era
In the time between the extinction of the Protheans and 580 BCE, all of the modern Citadel races in Mass Effect and other forms of intelligent life in the Milky Way evolve. In this time, Krogan civilization advances to the nuclear age until a global conflict thrusts their home world Tuchanka into a nuclear winter and Krogan society devolves into scattered and warring tribal factions. Around 580 BCE, the Asari discover faster-than-light travel thanks to the discovery of Prothean technology, and begin using the Mass Relays to explore the galaxy. They find and settle the Citadel, which they believe to be a Prothean creation, and 60 years later are joined by the Salarians, who independently discovered the space station as well.
Meanwhile, in the Andromeda Galaxy circa 1,600 BCE, a highly advanced race known as the Jardaan succeed in two creations: the Angara, an organic race, and the Remnant, a machine hive-mind. The reasons for creating the Angara are unknown, but they are the only sapient, native race of the Heleus Cluster that the Andromeda Initiative will encounter, and provide Mass Effect: Andromeda with its best character. The Remnant, on the other hand, seem to have been created for terraforming purposes throughout Andromeda. After an unknown disaster or conflict unleashes a dangerous phenomena known as the Scourge throughout the Heleus Cluster, the Jardaan leave Andromeda, and have yet to return as of the ending of Mass Effect: Andromeda.
Mass Effect Timeline - Founding of the Council & the Rachni Wars
In 500 BCE the Citadel Council is officially formed by the Asari and Salarians, who declare Mass Effect's Citadel as the central hub for the growing galactic community. 200 years later, circa 300 BCE, the Volus begin exploring the galaxy after discovering FTL space travel, and first contact is made by the Council. The Volus are contracted to create the Unified Banking Act, which establishes the Credit as the standardized galactic currency. The Volus are granted an embassy on the Citadel and not a Council seat, much to their chagrin.
Between 300 BCE and 1 CE on Mass Effect's timeline, first contact is made with the Batarians, Hanar, and Quarians; all of which are granted an embassy. The Asari also discover the Elcor homeward, help them to activate a nearby Mass Relay, and the Elcor are brought into galactic society through the quick establishment of a trade route to the Citadel.
In 1 CE, a Citadel expedition through a once-dormant mass relay leads to the discovery of the Rachni, a hostile species of hive-mind insects. Diplomacy proves impossible, since communication cannot be established with the Rachni queens deep below ground on their home world. After roughly 80 years of war with the Rachni, the Salarians make first contact with the Klingon-inspired Krogan, intent on uplifting them to interstellar status in order to serve as weapons against the Rachni.
The resilient Krogan, shaped by their difficult existence on war-torn and irradiated Tuchanka, are able to survive the environments of the Rachni worlds, and systematically eliminate the Rachni queens in their nests. The Rachni Wars come to a close in 300 CE when the Rachni are declared extinct, although they re-emerge over 2,000 years later during the events of Mass Effect on Noveria, one of the many planets receiving improved graphics in the Legendary Edition.
Mass Effect Timeline - Spectres and the Krogan Rebellions
For their role in the Rachni Wars, Mass Effect's Krogan are granted a new home world by the Citadel Council and they begin to colonize many planets as their population rapidly expands. In response to concerns over the growing and increasingly violent Krogan population, the Citadel Council forms the Special Tactics and Reconnaissance unit. These agents, known as Spectres, have incredible authority, answering only to the Council, and can carry out the Council's will at their discretion. A Salarian known as Beelo Gurji was made the first Spectre in 693 CE.
Around 700 CE, the Krogan Rebellions begin when the Spectres launch a preemptive strike on a Krogan clan aggressively annexing territory from an Asari colony on the planet Lusia. Overwhelmed by the rapidly replenished forces of the Krogan, the Council makes first contact with the Turians, a spacefaring race that had discovered several Mass Relays near their home world of Palaven and other colony planets. The Turians are enlisted in the Krogan Rebellions, and their colonies become the target of multiple Krogan offensives, suffering massive destruction.
Seeing no hope of victory against a race that can repopulate so fast, a group of Salarians (including Mass Effect 2 and 3's Mordin Solus) begin exploring bio-weapon solutions. Eventually the Genophage is created in 710 CE. The Genophage creates a genetic mutation within the Krogan, rendering viable Krogan pregnancies extremely rare, with many being stillborn. Because of the Genophage and the continued military efforts by the Turians, the Krogan population begins a steady decline and the Rebellions are ended by 800 CE.
Mass Effect Timeline - Humanity Reaches the Stars
Council space continued to expand throughout the ancient eras of human history in Mass Effect's timeline. Around 1600 CE, a mysterious race, which would later be known as the Collectors, are spotted in the Terminus Systems, which lie on the other side of the Milky Way from Council space - the area that would later be colonized by the Earth Systems Alliance. The Collector sightings are dismissed as fantasy due to no substantial evidence.
In the late 19th and early 20th centuries CE, Mass Effect's Citadel races become embroiled in a war with the Geth, a machine race created by the Quarians. When the Quarians became frightened by their creation and began disassembling them, the Geth revolted and claimed the Quarian worlds for themselves in The Geth War. Oddly, the Geth did not expand beyond the worlds they took from the Quarians, and the Quarians were relegated to becoming a nomadic people, living in space aboard the Migrant Fleet from which Mass Effect squad mate Tali hails. The Quarians' embassy on the Citadel was stripped from them for their creation of the Geth.
In 1961, Yuri Gagarin becomes the first human to travel through space, and eight years later the Apollo 11 mission lands on the Moon. Over the next 100 years in Mass Effect's history, humanity explores the Sol system before Armstrong Outpost is founded as the first Lunar human settlement in 2069 on the 100th anniversary of the Apollo 11 landing. In 2103, the European Space Agency creates the first permanent settlement on Mars. In 2143, Humans construct Gagarin Station beyond Pluto's orbit where early attempts at FTL travel are conducted.
In 1247, Element Zero is discovered on Mars. Element Zero is the instrumental component in creating "Mass Effect" fields that allow FTL travel. One year later, Prothean ruins are discovered on Mars and propel humanity into the interstellar age. It is discovered in 2149 that Pluto's moon Charon is actually a Mass Relay encased in ice. Discovery of the Mass Relay network leads the 18 largest nations on Earth to form the Earth Systems Alliance, a military and exploratory organization. Five years later, Mass Effect's Commander Shepard is born on April 11, 2154.
Mass Effect Timeline - The First Contact War and Beyond
In 2157 in Mass Effect's history Turians discover a team of Human explorers attempting to activate a dormant Mass Relay, a practice that was outlawed by the Council following the disastrous activation of the Relay that led to Rachni space. The Humans and Turians enter a conflict that lasts for three months known to the humans as The First Contact War; Turians refer to it as the Relay 314 Incident. Much of the conflict surrounds the Human colony of Shanxi, which falls to the Turians, but is later recovered by the Humans. Before the conflict can escalate further, the Citadel Council steps in and brokers peace, introducing Humans to the larger galactic community.
The First Contact War affects many characters, especially Turians, that Commander Shepard interacts with in the games, and specifically comes up when getting to know Garrus in Mass Effect. Many humans are irreparably influenced by the conflict as well. Convinced of an inevitable conflict with aliens, Human Jack Harper founds the human-survivalist paramilitary group known as Cerberus, publishing a manifesto and donning the moniker of the Illusive Man. Cerberus is largely ignored by the galactic media, but will come to be instrumental in the events of Mass Effect 2 and 3.
A mysterious artifact is found in 2162 near the Perseus Veil, which is later revealed to be Sovereign, the Reaper vanguard which hibernates until it detects the sufficient advancement of organic species to begin the next harvest. In 2163, the Ryder twins are born, who will later become the human Pathfinders for the Andromeda Initiative and serve as protagonists in Mass Effect: Andromeda. In the same year, the Leviathan of Dis - the Reaper that was destroyed 37 million years ago - is discovered on the planet Jartar before disappearing under mysterious circumstances. It will later be revealed that it was smuggled away for study by Batarian scientists, who became indoctrinated by the Reaper they were studying.
After rapid expansion throughout the galaxy, Humanity is granted an embassy on the Citadel in 2165. Around the same time, David Anderson - the first N7 operative, veteran of the First Contact War, and original commander of the SSV Normandy - launches an investigation alongside Saren, a Turian Spectre, into the illegal use of AI to investigate the dormant Sovereign. Saren sabotages the mission, blames Anderson for its failure, and seizes the AI research for himself.
Between 2165 and the beginning of Mass Effect in 2183, many conflicts between the Earth Systems Alliance and Batarian pirates occur after the Council refused to limit Human expansion into Batarian territory, which prompted the Batarians to dissolve their embassy on the Citadel. In this time, Cerberus also becomes a terrorist threat throughout the galaxy, with notable operations that include stealing antimatter from an Alliance cruiser and sponsoring a number of high-profile assassinations on Earth, including a Pope in 2171.
In 2176, the Andromeda Initiative begins, which will send colonists from multiple Milky Way races to the Andromeda Galaxy. The SSV Normandy is created as a joint effort between Turians and Humans. David Anderson is made commander of the Normandy, with Shepard serving as his executive officer. The first mission of the SSV Normandy is to extract a Prothean beacon from the planet Eden Prime, the events of which make up the beginning of the first Mass Effect.