Mass Effect Universe Primer >


Waiting for JavaScript...

Galactic Regions

Citadel Space

Citadel Space Factbox
[Mass Effect Wiki]

Citadel Space is the informal name for all territories under the jurisdiction of Council law. Citadel Space is composed of the regions of space controlled by the governments of the Council’s member and associate species.

Although a glance at the galaxy map shows Council Space stretching across most of the Milky Way’s volume, the truth is that Council Space consists of a relative handful of densely developed star clusters, connected to one another by the Mass Relay system. Of the galaxy’s 100 billion stars, only a tiny fraction are part of Council Space.

Worlds like Noveria and Illium are excluded from Citadel Space: while they are dominated by species with Citadel membership, they are nonetheless controlled by private interests, not by governments.

Attican Traverse

Attican Traverse Factbox
[Mass Effect Wiki]

The Attican Traverse is an largely-unsettled frontier region of the galaxy. Humans have made significant inroads in colonizing the region, but the Traverse lies close to the Terminus Systems, making colonization risky.

Terminus Systems

Terminus Systems Factbox
[Mass Effect Wiki]

The Terminus Systems are a lawless expanse of the galaxy, largely controlled by pirates and mercenary gangs. Organizations operating out of the Terminus frequently conduct pirate raids and slave grabs on neighboring territory.

Although the Terminus as a whole is lawless, some regions have some semblance of civilization to them. Omega is a relatively stable nexus of commerce, and Illium is an asari border world, specializing in the trade of products illegal in Citadel Space. In contrast, the Nemean Abyss is a particularly lawless region, largely inhabited by batarian pirates.

Galactic Core

Galactic Core Factbox
[no wiki link available]

The Galactic Core is the central region near the Milky Way galaxy’s supermassive black hole. The core is dominated by black holes and violent stars, which bathe the region in X-rays and other radiation. It is generally believed that no life can survive for long in the core, as the necessary shielding is beyond standard galactic technology.

Despite all this, the Galactic Core contains the Collector Base, a large, shielded space station orbiting a black hole.

Dark Space

Dark Space Factbox
[Mass Effect Wiki]

Dark Space is the informal name for the space between galaxies. The Reapers hibernate in Dark Space between their Harvests, using the Citadel as a mass relay to travel between Dark Space and the Milky Way galaxy.

Major Ships, Stations, and Planets

Normandy SR-1

Normandy SR-1 Factbox
 Region: varies
Cluster: varies
 System: varies
   Type: ship
[Mass Effect Wiki]

The SSV Normandy SR-1 is an Alliance frigate built as a human-turian joint venture. It possesses a prototype stealth system, which makes it capable of concealing its heat signature for several hours at a time. When ME1 begins, the Normandy is under the command of Captain Anderson. Shortly afterward, Anderson steps down and command is transferred to Commander Shepard.

The Normandy SR-1 is destroyed in the opening events of ME2.

Normandy SR-2

Normandy SR-2 Factbox
 Region: varies
Cluster: varies
 System: varies
   Type: ship
[Mass Effect Wiki]

The Normandy SR-2 is a Cerberus frigate modeled after the Normandy SR-1, including its prototype stealth technology. The SR-2 is also equipped with an AI, EDI, who operates the ships electronic warfare and cyberwarfare suites.

During the opening events of ME2, Cerberus provides Shepard with the SR-2 for the purpose of stopping the Collectors from abducting human colonists. Between ME2 and ME3, Shepard surrenders the SR-2 to the Alliance, but regains command of the ship when Shepard is reinstated as Commander in the opening events of ME3.

The Citadel

The Citadel, partially obscured by the Serpent Nebula
 Citadel Factbox
 Region: Citadel Space
Cluster: Serpent Nebula
 System: Widow
   Type: station
[Mass Effect Wiki]

The Citadel is an enormous space-station-cum-city orbiting the star Widow in the Serpent Nebula. It is an O'Neill Cylinder consisting of five arms and five gaps, each 45km long and held in place to form a cylinder 13km in diameter. The arms can fold closed to form a cylinder of smaller diameter, which is useful for protecting the station when it comes under attack. It has a population of 13.2 million.

As with the mass relays, received wisdom has it that the Citadel was built by the Protheans. In truth, it was built by the Reapers as a honeypot: spacefaring civilizations are naturally attracted to its technological marvels and its defensible position, making the Citadel a natural capitol for their empires. However, it is actually a giant dormant mass relay, linking to the site in Dark Space where the Reapers hibernate. When the Citadel relay is activated, the Reapers normally come pouring through, decapitating whichever government happens to hold it. This process was sabotaged by the Protheans after they themselves fell victim to the trap, thus giving the modern cycle a fighting chance against the Reapers.

During the events of ME3, the Citadel is relocated from the Serpent Nebula to orbit around Earth. How this is done is not explained.


 Thessia Factbox
 Region: Citadel Space (asari space)
Cluster: Athena Nebula
 System: Parnitha
   Type: planet (asari homeworld)
[Mass Effect Wiki]

Thessia is the ecologically rich garden world which the asari call home. Thessia enjoys a stable economy backed by wealthy colonies and abundant reserves of eezo. Eezo is so common that Thessian life has adapted to its presence: for instance, asari mothers-to-be who do not live on the homeworld must take eezo supplements during pregnancy.

Thessia has no unified government, and is instead composed of many independently sovereign city-state republics. Most such republics practice e-democracy, a form of direct democracy wherein citizens directly propose laws and vote on them via the Extranet.


Sur’Kesh Factbox
 Region: Citadel Space (salarian space)
Cluster: Annos Basin
 System: Pranas
   Type: planet (salarian homeworld)
[Mass Effect Wiki]

Sur’Kesh, a garden world orbiting Pranas in the Annos Basin, is the salarian homeworld. Hosting large oceans, a humid climate, and lush vegetation, the world is home to many rainforests with rich biodiversity. The world was once threatened by pollution and overpopulation, but the salarians put their minds toward developing ways to thrive without destroying their habitat, and now live in sustainable balance.


 Palaven Factbox
 Region: Citadel Space (turian space)
Cluster: Apien Crest
 System: Trebia
   Type: planet (turian homeworld)
[Mass Effect Wiki]

Palaven is a dextro-amino garden world orbiting Trebia in the Apien Crest. It is the turian homeworld. Palaven has a weaker magnetic field than most garden worlds, allowing more solar radiation to reach the surface. The native life has evolved to adapt to this condition: for example, plants shut down non-essential metabolic pathways during the day and engage in DNA repair at night.


Tuchanka Factbox
 Region: Citadel Space
Cluster: Krogan DMZ
 System: Aralakh
   Type: planet (krogan homeworld)
[Mass Effect Wiki]

Tuchanka, located in orbit around Aralakh in the Krogan DMZ, is the krogan homeworld. It is a post-apocalyptic wasteland, devastated by nuclear war conducted long before the krogan were uplifted to space travel. Tuchanka is a world out of balance, with precious little plant life and runaway warming; the salarians created a shroud at the L1 Lagrange point to shield the planet from the full brunt of Aralakh’s glare.


 Rannoch Factbox
 Region: Terminus Systems
Cluster: Perseus Veil
 System: Tikkun
   Type: planet (quarian homeworld)
[Mass Effect Wiki]

Rannoch is a dextro-amino garden world and the ancestral homeworld of the quarians. It orbits the star Tikkun in the Perseus Veil, a position that places it on the edge of the Terminus Systems. As Rannoch is a relatively hot and arid desert world, life there is concentrated around the sparse rivers and oceans. Rannoch’s name is Khelish for “walled garden”, reflecting the importance of plants and shade to quarian culture.

As of 2183, the geth are the only intelligent life on Rannoch, having driven the quarians to exile 300 years ago.


Khar’shan Factbox
 Region: Citadel Space (Alliance space)
Cluster: Kite’s Nest
 System: Harsa
   Type: planet (batarian homeworld)
[Mass Effect Wiki]

Khar’shan, a garden world orbiting Harsa in the Kite’s Nest cluster, is the batarian homeworld. Due to information control and propaganda by the Batarian Hegemony, little about the planet is known to outsiders. Khar’shan was the first world to fall to the Reapers in the war, having been conquered shortly before the start of ME3.


   Omega Factbox
 Region: Terminus Systems
Cluster: Omega Nebula
 System: Sahrabarik
   Type: station
[Mass Effect Wiki]

Omega is a space station built into a mined-out asteroid, population 7.8 million. The asteroid orbits the star Sahrabarik in the Omega Nebula, deep in the Terminus Systems. It is currently ruled by Aria T’Loak with an iron fist, making it a relatively stable nexus for trade and commerce.


  Illium Factbox
 Region: Terminus Systems
Cluster: Crescent Nebula
 System: Tasale
   Type: planet (garden world)
[Mass Effect Wiki]

Illium is a garden world orbiting the star Tasale in the Crescent Nebula. Controlled by asari corporate interests but not technically part of asari space, it operates outside Council law as the asari gateway to the Terminus Systems, serving as a significant trade hub. Many items that are illegal in Citadel Space, such as slaves and mind-altering drugs, are merely regulated on Illium.

The Collector Base

Collector Base Factbox
  Region: Galactic Core
 Cluster: unknown
  System: unknown
    Type: station
[Mass Effect Wiki]

The Collector Base is the effective “homeworld” of the Collectors. Located in the Galactic Core, the base orbits a black hole and is surrounded by an enormous debris field composed of the wrecked ships of those who attempted to use the Omega-4 relay and failed.

Minor Ships, Stations, and Planets

Arcturus Station

Arcturus Station Factbox
 Region: Citadel Space
Cluster: Arcturus Stream
 System: Arcturus
 Planet: Themis
   Type: station (destroyed)
[Mass Effect Wiki]

Arcturus Station was a human space station located at the L5 Lagrange point of the gas giant Themis and its parent star Arcturus in the Arcturus Stream. It was a 5km-diameter ring of Stanford Torus design, and it was the the capitol of the Systems Alliance and seat of the Systems Alliance Parliament.

Arcturus Station was destroyed in the opening shots of the Reaper War.

The Migrant Fleet

 Migrant Fleet Factbox
 Region: varies
Cluster: varies
 System: varies
   Type: flotilla
[Mass Effect Wiki]

The Migrant Fleet is a flotilla of approximately 50,000 ships in various states of repair. It is the home-in-exile of the quarian species.

Eden Prime

    Eden Prime Factbox
 Region: Citadel Space (Alliance space)
Cluster: Exodus Cluster
 System: Utopia
   Type: planet (garden world)
[Mass Effect Wiki]

Eden Prime is humanity’s most prosperous colony world; it orbits the star Utopia in the Exodus Cluster. In terms of land use, it is primarily an agricultural world, but it has populous cities contained in vertical arcologies.

Eden Prime was once a Prothean world, and a number of Prothean ruins and artifacts are discovered there over the course of the games.

Terra Nova

   Terra Nova Factbox
 Region: Citadel Space (Alliance space)
Cluster: Exodus Cluster
 System: Asgard
   Type: planet (garden world)
[Mass Effect Wiki]

Terra Nova is the oldest human colony world outside of the Sol system, and it orbits the star Asgard in the Exodus Cluster. It has extensive deposits of platinum. Asteroid X57 was recently inserted into orbit around Terra Nova, by strapping fusion torches to the asteroid to accelerate it into place. In ME1 [Bring Down the Sky DLC], batarian terrorists hijack the asteroid and attempt to cause a planetary extinction event by crashing it into the capitol city.


  Therum Factbox
 Region: Citadel Space (Alliance space)
Cluster: Artemis Tau
 System: Knossos
   Type: planet (post-garden world)
[Mass Effect Wiki]

Therum is a human industrial world orbiting the star Knossos in the Artemis Tau cluster. Tectonically active and rich with minerals, there is evidence that Therum was more habitable in the past, and Therum is dotted with Prothean ruins.


   Feros Factbox
 Region: Citadel Space (Alliance space)
Cluster: Attican Beta
 System: Theseus
   Type: planet (garden world)
[Mass Effect Wiki]

Feros is a human-controlled habitable world orbiting the star Theseus in the Attican Beta cluster. Two-thirds of the planet’s land area is covered by Prothean ruins, the remnants of megalopolies. ExoGeni Corporation funds and operates a small colony in the ruins, tasked with exploration. Feros was home to the Thorian, a unique plant-based intelligence many thousands of years old.


 Noveria Factbox
 Region: Citadel Space (Alliance space)
Cluster: Horse Head Nebula
 System: Pax
   Type: planet (marginal garden world)
[Mass Effect Wiki]

Noveria is a bitterly cold human-controlled world orbiting the star Pax in the Horse Head Nebula. While controlled by human interests, it is privately owned and operated outside the reach of Council law. It is home to R&D labs performing corporate research too secret, too dangerous, or too controversial to be carried out elsewhere.


 Virmire Factbox
 Region: Attican Traverse
Cluster: Sentry Omega
 System: Hoc
   Type: planet (garden world)
[Mass Effect Wiki]

Virmire is a lush, uncolonized frontier world orbiting Hoc in the Sentry Omega cluster. While ecologically ripe for colonization, it lies too close to the Terminus Systems to make it an attractive colony world.


    Ilos Factbox
 Region: Terminus Systems
Cluster: Pangaea Expanse
 System: Refuge
   Type: planet (late-stage garden world)
[Mass Effect Wiki]

Ilos is a devastated late-stage garden world orbiting the star Refuge in the Pangaea Expanse. It is located in the Terminus Systems. Ilos was once a major Prothean world, but was presumably devastated by the Reapers 50,000 years ago.

Ilos was the home to a secret Prothean research facility, the location of which was successfully kept secret from the Reapers. The researchers, who had been studying mass relay technology, went into cryogenic stasis to wait out the Reaper invasion, then built the Conduit and disabled the Citadel’s function as a mass relay to Dark Space.