Mass Effect Timeline: every major event from the Leviathans to Andromeda

This timeline covers the Mass Effect universe from the Leviathans' rule over the early galaxy to the Andromeda Initiative's arrival in the Heleus Cluster. Dates use the Gregorian calendar, BCE and CE, as the in-game codex does. Anything older than recorded history comes from the trilogy's characters and archives, so those dates are rounded and labelled "around". The original trilogy runs from 2183 to 2186 (BioWare, 2007 to 2012), and Mass Effect: Andromeda (2017) is set in 2819.

The deep past (before around 125,000 BCE)#

Nothing in this era has a firm date. What the galaxy knows of it comes from the Leviathans themselves, from Vigil on Ilos and from the wreckage of dead machines.

• Unknown date: The Leviathans were the galaxy's dominant species. They ruled the younger races they found as thralls and protected them in exchange. They saw that their subject races kept building synthetic life that rose up and destroyed its makers, so they created an artificial Intelligence to find a way to preserve organic life. (Mass Effect 3: Leviathan)
• Unknown date: The Intelligence decided the answer was to harvest advanced organics and store them in machine form. It turned on its creators and made the first Reaper in the Leviathans' image, and the harvests began. The handful of Leviathans who survived hid in the oceans of remote worlds. (Mass Effect 3: Leviathan; Mass Effect 3)
• Unknown date: The Reapers left the Citadel and the mass relay network for each new cycle to find. Younger species built their civilisations around the relays, which meant they developed along paths the Reapers could predict. The keepers, apparently harmless caretakers aboard the Citadel, were part of the same design. (Mass Effect)
• Around 1 billion years ago: A Reaper was killed and its corpse came to rest on the planet Jartar in the Dis system. It lay there undisturbed until a batarian survey team found it in 2163. (Mass Effect; Mass Effect 3: Leviathan)
• Around 37 million years ago: An unknown species fired a mass accelerator round through a Reaper near the gas giant Mnemosyne. The shot disabled the machine and carried on into space until it struck the planet Klendagon and gouged out a great rift. (Mass Effect 2)
• Every 50,000 years or so: The cycle repeated. Each time a galactic civilisation reached its peak, the Reapers arrived from dark space, harvested or destroyed every advanced species and withdrew to wait again. (Mass Effect)

Extinct empires and the Protheans (around 125,000 to 48,000 BCE)#

Several dead civilisations left traces the modern galaxy could study. The best known by far are the Protheans, whose ruins and technology shaped everything that came after.

• Around 125,000 BCE: Two spacefaring species, the inusannon and the thoi'han, fought over the garden world Eingana. The wrecks of their fleets still litter its surface, and element zero leaking from broken drive cores altered the planet's native life. (Mass Effect 2)
• Before 48,000 BCE: The Protheans built an empire across the galaxy with the Citadel as its capital. They fought and won the Metacon War against a hostile machine intelligence, then bound the other species of their cycle into a single empire under Prothean rule. (Mass Effect; Mass Effect 3: From Ashes)
• Before 48,000 BCE: The Protheans kept watch over younger species with promise. They studied early humans from an observation post on Mars and quietly guided the primitive asari, leaving a Prothean beacon hidden on Thessia. (Mass Effect; Mass Effect 3)
• Around 48,000 BCE: The Reapers arrived through the Citadel, which was itself a giant mass relay. They cut off the Prothean leadership at a stroke and seized the relay network, then spent centuries taking the empire apart system by system. (Mass Effect)
• Around 48,000 BCE: A small team of Prothean scientists survived on the research world Ilos. They used a prototype relay called the Conduit to reach the Citadel and altered the keepers so they would ignore the next Reaper signal, then died out. The virtual intelligence Vigil stayed behind to warn whoever came next. (Mass Effect)
• Around 48,000 BCE: The Prothean soldier Javik went into a stasis pod on what would later become Eden Prime, meant to wake a new generation of his people. He would sleep for 50,000 years. (Mass Effect 3: From Ashes)

The early Council (580 BCE to 1 CE)#

The modern galactic community began when the asari reached the Citadel. The firm dates from here come from the Citadel timeline in Galactic Codex: Essentials, the booklet BioWare packed with the Mass Effect Limited Collector's Edition.

• 580 BCE: Having learned to travel faster than light from Prothean ruins, the asari explored the relay network and found the Citadel, already tended by the keepers. (Mass Effect, codex; Galactic Codex: Essentials)
• 520 BCE: The salarians reached the Citadel and opened relations with the asari. (Mass Effect, codex; Galactic Codex: Essentials)
• 500 BCE: The asari and the Salarian Union founded the Citadel Council. The station became the political centre of the galaxy. (Mass Effect, codex; Galactic Codex: Essentials)
• After 500 BCE: The volus became the first species after the founders to gain an embassy on the Citadel. They drafted the Unified Banking Act, which created the credit as a common galactic currency. (Mass Effect, codex)
• Before 1 CE: The elcor and the hanar joined the Citadel community, and the quarians also gained an embassy. (Mass Effect, codex)

The Rachni Wars and the Krogan Rebellions (1 to 900 CE)#

Opening dormant relays brought the Council two wars in a thousand years. The second ended with a weapon whose effects were still killing krogan in Shepard's time.

• Around 1 CE: A Citadel expedition opened a dormant relay and met the rachni, a hive-minded insectoid species who attacked at once. The queens lived deep underground on toxic worlds and could not be reached for talks, and the Rachni Wars began. (Mass Effect, codex; Galactic Codex: Essentials)
• Around 80 CE: The salarians found the krogan on Tuchanka, a world they had wrecked in their own nuclear wars. They gave the krogan spaceflight and sent them into the rachni nests, where they hunted down the queens one by one. (Mass Effect, codex; Galactic Codex: Essentials)
• 300 CE: The rachni were declared extinct. As a reward the Council gave the krogan new worlds, and the Council banned the opening of dormant relays so nothing like the rachni could be let loose again. (Mass Effect, codex; Galactic Codex: Essentials)
• 300 to 700 CE: Freed from Tuchanka's hostile ecology, the krogan multiplied fast and spread to world after world. (Mass Effect, codex)
• Around 700 CE: Krogan settlers moved onto the asari world Lusia and refused to withdraw. That refusal started the Krogan Rebellions. The Council brought in the newly contacted turians, and the krogan answered with weapons of mass destruction on turian colonies. (Mass Effect, codex; Galactic Codex: Essentials)
• 710 CE: The turians deployed the genophage, a salarian bioweapon that left only one krogan pregnancy in a thousand viable. It broke the krogan war machine within a few generations. (Mass Effect, codex; Galactic Codex: Essentials)
• Around 800 CE: The Rebellions ended, though krogan holdouts kept fighting for decades. The Citadel Conventions came out of the war to regulate weapons of mass destruction. (Mass Effect, codex; Galactic Codex: Essentials)
• 900 CE: The Turian Hierarchy became the third member of the Council and took over the galaxy's peacekeeping role. Under the Treaty of Farixen the turians were allowed the largest dreadnought fleet of any species. (Mass Effect, codex; Galactic Codex: Essentials)

The Morning War and the quiet centuries (900 to 2147 CE)#

The galaxy was mostly at peace for a thousand years. Its biggest upheaval came from a machine race the quarians built themselves.

• Around 1600 CE: The first reports of the Collectors came out of the Terminus Systems. Citadel space wrote them off as tall tales. (Mass Effect 2, codex)
• 1895 CE: The geth, machines the quarians built for labour, began asking whether they had souls. The quarians tried to shut them down, and the geth fought back in the Morning War. Within a year the quarians had lost Rannoch and every one of their colonies. (Mass Effect, codex; Mass Effect 3)
• 1895 CE: The surviving quarians took to their ships as the Migrant Fleet. The Council blamed them for the geth and closed their embassy, and the geth withdrew behind the Perseus Veil and were not seen in Citadel space for almost three centuries. (Mass Effect, codex; Galactic Codex: Essentials)
• 2069 CE: Armstrong Outpost was founded on Luna as the first permanent human settlement off Earth. (Mass Effect, codex)
• 2103 CE: Lowell City on Mars became the first permanent human settlement there. (Mass Effect, codex)
• 2125 CE: Citadel surveyors found the yahg on Parnack. The yahg killed the Council's delegation, and Parnack was put off limits. One captured yahg later rose through the Shadow Broker's network and took the Broker's place. (Mass Effect 2: Lair of the Shadow Broker)

Humanity reaches the stars (2148 to 2182 CE)#

Human history in the galaxy moved fast. Within forty years of finding the Mars ruins, humans had fought a war with the turians, won an embassy on the Citadel and come close to a Council seat.

• 2148: Explorers found a cache of Prothean technology beneath the Martian surface. Decoding it gave humanity mass effect physics and faster-than-light travel. (Mass Effect, codex)
• 2149: The Prothean data led humans to Charon, Pluto's moon, which turned out to be a dormant mass relay encased in ice. Jon Grissom led the first crew through it to Arcturus. The same year Earth's largest nations signed the charter of the Systems Alliance to direct humanity's expansion and defence. (Mass Effect, codex; Mass Effect: Revelation)
• 2150 to 2156: The Alliance's first surveys found colony worlds including Terra Nova. Work began on Arcturus Station in 2151, and the station was inaugurated as Alliance headquarters in 2156. (Mass Effect, codex)
• 2154: Shepard was born on 11 April. (Mass Effect)
• 2157: A turian patrol caught a human crew trying to open Relay 314, which Council law had forbidden since the Rachni Wars, and opened fire. The First Contact War followed. The turians took Shanxi, the Alliance retook it a month later, and the Council stepped in to broker peace before the fighting could spread. (Mass Effect, codex; Mass Effect: Revelation)
• 2157: During the occupation of Shanxi, the mercenary Jack Harper came into contact with an ancient alien artefact that left its mark on him. He came out of the war set on making humanity strong enough to stand alone, the start of the road to Cerberus and his life as the Illusive Man. (Mass Effect: Evolution)
• 2165: The Council gave humanity an embassy on the Citadel. The same year an attack on a secret Alliance research base at Sidon put Lieutenant David Anderson and Kahlee Sanders on the trail of the killers. Anderson's bid to become the first human Spectre failed after he was paired with Saren Arterius, and Saren found the derelict ship later known as Sovereign. (Mass Effect, codex; Mass Effect: Revelation)
• 2170: Batarian slavers raided the human colony of Mindoir and killed or captured many of its people. (Mass Effect)
• 2171: The batarians demanded that the Council keep humans out of the Skyllian Verge. When it refused, the Batarian Hegemony closed its embassy and withdrew from Citadel society. (Mass Effect, codex)
• 2176: Pirates and slavers backed by batarian money attacked Elysium in the Skyllian Blitz. The defenders held until the Alliance fleet drove the raiders off. (Mass Effect)
• 2176: Jien Garson founded the Andromeda Initiative, a privately funded plan to send colonists from several species to the Andromeda galaxy. (Mass Effect: Andromeda)
• 2177: A fifty-strong Alliance marine unit was wiped out by thresher maws on Akuze. (Mass Effect)
• 2178: The Alliance hit back for the Blitz with an assault on the batarian-backed criminal bases on the moon Torfan. (Mass Effect)

The Eden Prime War (2183 CE)#

The first year of the trilogy. A geth army returned after three hundred years, led by a Council Spectre who had already fallen under Reaper control.

• 2183: The Alliance and the turians built the stealth frigate Normandy SR-1. Captain Anderson took command, with Commander Shepard as his executive officer. (Mass Effect)
• 2183: The geth attacked Eden Prime and started the Eden Prime War. Saren killed the turian Spectre Nihlus Kryik there, and a Prothean beacon dug up on the colony burned visions of the Reapers into Shepard's mind. (Mass Effect)
• 2183: The Council revoked Saren's status and made Shepard the first human Spectre. Shepard tracked Saren across Feros, where the Thorian controlled the colonists, and Noveria, where Matriarch Benezia had found a living rachni queen. Benezia's daughter Liara T'Soni joined the Normandy. (Mass Effect)
• 2183: The batarian terrorist Balak tried to drop asteroid X57 onto Terra Nova and was stopped. (Mass Effect: Bring Down the Sky)
• 2183: On Virmire, Shepard's team destroyed Saren's research base, where he was trying to breed a cure for the genophage. The base was levelled with a nuclear device, at the cost of either Kaidan Alenko or Ashley Williams. There Sovereign revealed itself as a Reaper. (Mass Effect)
• 2183: On Ilos, Vigil told Shepard how the Protheans fell. Saren used the Conduit to reach the Citadel and tried to open the station for the Reapers. In the Battle of the Citadel, Saren died, and the Alliance fleet and the Normandy destroyed Sovereign. Humanity was given a seat on the reformed Council. (Mass Effect)
• 2183: About a month later, a Collector ship destroyed the Normandy over Alchera. Shepard was killed. (Mass Effect 2)
• 2183: Liara and the drell agent Feron recovered Shepard's body from the Shadow Broker's agents and handed it to Cerberus, which began the Lazarus Project to bring Shepard back. (Mass Effect: Redemption)
• 2183: Cerberus targeted the Ascension Project's young biotics at Grissom Academy and tried to exploit the Migrant Fleet. Its plans were wrecked by Kahlee Sanders and the defector Paul Grayson. (Mass Effect: Ascension)

The Collector campaign (2184 to 2185 CE)#

With Shepard dead and the Council treating the Reapers as Saren's invention, the Reapers worked through proxies. The Collectors began taking whole human colonies.

• 2183 to 2185: Alliance special forces defended the colony of Fehl Prime from Blood Pack mercenaries. In 2185 the Collectors attacked it, and James Vega chose to save intelligence on the Collectors over the colonists. (Mass Effect: Paragon Lost)
• Before 2185: Cora Harper joined the Andromeda Initiative and helped recover stolen Initiative technology before launch. (Mass Effect: Andromeda: Initiation)
• 2185: Two years after the Normandy fell, Cerberus revived Shepard. With the Normandy SR-2, Shepard confirmed that the Collectors were taking colonists and witnessed their attack on Horizon. The crew learned that the Collectors were the remains of the Protheans, rebuilt by the Reapers. (Mass Effect 2)
• 2185: Tali'Zorah's father Rael'Zorah died aboard a quarian ship after reactivating geth in secret experiments. The geth platform Legion joined the Normandy. (Mass Effect 2)
• 2185: Shepard's crew went through the Omega 4 Relay and destroyed the Collectors and the human Reaper they were building. (Mass Effect 2)
• 2185: Liara found the Shadow Broker's ship on Hagalaz, killed the yahg Broker and took over his network. (Mass Effect 2: Lair of the Shadow Broker)
• 2185: The Andromeda Initiative launched. The Nexus and four arks, including the human ark Hyperion, left for the Heleus Cluster. (Mass Effect: Andromeda)

The Reaper War (2186 CE)#

The Reapers arrived through batarian space and attacked Earth within months. Every major species was dragged in, and the war ended at the Citadel over Earth.

• 2185 to 2186: Shepard found Alliance scientist Amanda Kenson on an asteroid in the Bahak system, where a Reaper artefact had shown her the invasion was close. To delay it, Shepard drove the asteroid into the Alpha Relay. The explosion destroyed the system and killed more than 300,000 batarians, and Shepard surrendered to the Alliance. (Mass Effect 2: Arrival)
• Before the invasion: Cerberus captured Paul Grayson and filled his body with Reaper technology. Kahlee Sanders and David Anderson tried to rescue him, and he died. His daughter Gillian later went after Cerberus for revenge and captured its assassin Kai Leng to draw out the Illusive Man. (Mass Effect: Retribution; Mass Effect: Deception)
• 2186: The quarian ark Keelah Si'yah left for Andromeda just after the Reapers struck batarian space. (Mass Effect: Andromeda: Annihilation)
• 2186: The Reapers overran batarian space, then hit Earth and the turian colony Taetrus. Shepard escaped Earth with Anderson's blessing and found plans for a Prothean superweapon, the Crucible, in the Mars archive. (Mass Effect 3)
• 2186: Shepard built a coalition for the Crucible. A cure for the genophage was spread from Tuchanka, Javik was woken on Eden Prime, and the war between the quarians and the geth over Rannoch came to a head. (Mass Effect 3; Mass Effect 3: From Ashes)
• 2186: Cerberus attempted a coup on the Citadel with Councillor Udina. Later that year Thessia fell, and Kai Leng took the Prothean data that named the Crucible's missing piece, the Catalyst. (Mass Effect 3)
• 2186: Shepard found the surviving Leviathans hiding on the ocean world 2181 Despoina and learned how the Reapers began. Aria T'Loak took Omega back from Cerberus. (Mass Effect 3: Leviathan; Mass Effect 3: Omega)
• 2186: The Catalyst turned out to be the Citadel, which the Reapers had moved to Earth. The combined fleets attacked, the Crucible docked, and Anderson and the Illusive Man both died aboard the station. Shepard faced the Intelligence that controlled the Reapers and made the choice that ended the Reaper War. (Mass Effect 3)

The long crossing (2186 to 2818 CE)#

While the Initiative's sleepers crossed dark space, the Heleus Cluster was changing in ways nobody in the Milky Way could see.

• Long before 2819: The Jardaan created the angara and seeded them across several worlds in the Heleus Cluster. Later, the Scourge tore through the cluster. It crippled the Remnant machines and threw the angara into a dark age. (Mass Effect: Andromeda)
• Around 2744: The kett invaded the Heleus Cluster to absorb the angara into their empire. Their commander, the Archon, also became fixated on controlling Remnant technology. (Mass Effect: Andromeda)
• Around 2753: More than five centuries into its voyage, sabotage planted before launch crippled the Keelah Si'yah and spread a deadly plague through its sleepers. A Sleepwalker team was woken to save the ship. (Mass Effect: Andromeda: Annihilation)
• 2814: Evfra de Tershaav merged the angara's scattered resistance movements into the Angaran Resistance, based on Aya. (Mass Effect: Andromeda)
• 2818: The Nexus reached the Heleus Cluster and ran straight into the Scourge. Most of its leaders died. Under Jarun Tann, the survivors faced a revolt over food and command, and when it ended Sloane Kelly led the exiles to Kadara and the krogan under Nakmor Kesh's clan left the station. (Mass Effect: Andromeda: Nexus Uprising; Mass Effect: Andromeda)

Mass Effect games in order#

The four main games came out in story order, so release order and chronological order match.

1. Mass Effect (2007)
2. Mass Effect 2 (2010)
3. Mass Effect 3 (2012)
4. Mass Effect: Andromeda (2017)

Andromeda is the odd one. Its colonists leave the Milky Way in 2185, between Mass Effect 2 and 3, but the game takes place in 2819 and doesn't need any of Shepard's story.

Story DLC in order#

1. Mass Effect: Bring Down the Sky (2008), during Mass Effect
2. Mass Effect 2: Lair of the Shadow Broker (2010), during Mass Effect 2 (playable before the final mission)
3. Mass Effect 2: Arrival (2011), the bridge into Mass Effect 3
4. Mass Effect 3: From Ashes (2012), during Mass Effect 3
5. Mass Effect 3: Leviathan (2012), during Mass Effect 3
6. Mass Effect 3: Omega (2012), during Mass Effect 3

For a first run, play the trilogy in order through Mass Effect Legendary Edition (2021), which bundles all three games and nearly all of this DLC and carries your choices from one game to the next. Play Andromeda afterwards, if at all.

Mass Effect books in story order#

1. Mass Effect: Revelation (2007), before Mass Effect
2. Mass Effect: Ascension (2008), after Mass Effect
3. Mass Effect: Retribution (2010), after Mass Effect 2
4. Mass Effect: Deception (2012), before the Reaper invasion
5. Mass Effect: Andromeda: Initiation (2017), before the Initiative launches
6. Mass Effect: Andromeda: Annihilation (2018), on the quarian ark's voyage
7. Mass Effect: Andromeda: Nexus Uprising (2017), on the Nexus before the Hyperion arrives

Where the story stands (2819 CE)#

The latest dated events in the chronology belong to the Andromeda Initiative's first year in Heleus. Nobody there knew how the Reaper War had ended.

• 2819: The Hyperion reached the Heleus Cluster about fourteen months after the Nexus, 634 years after leaving the Milky Way. Pathfinder Alec Ryder died on Habitat 7, and one of his twin children inherited the role along with the AI SAM. (Mass Effect: Andromeda)
• 2819: The new Pathfinder founded the outpost Prodromos on Eos, made contact with the angara and rescued Moshae Sjefa from the kett on Voeld. The Initiative also opened outposts on Kadara and Elaaden. (Mass Effect: Andromeda)
• 2819: The Pathfinder found the Remnant world Meridian and defeated the Archon there. The Initiative and the angara now had a foothold in Heleus, and the other arks were still unaccounted for, including the Keelah Si'yah. (Mass Effect: Andromeda)