Wayfarer swimming
Image from Chris Shaeffer

As Terragen civilization has spread into the galaxy, it has encountered both living aliens and the remains of extinct aliens. Some of them once built vast empires but have since vanished but for a few enigmatic traces, and indeed had been gone for millions of years before life even crawled up on dry land on Earth.

Telescopic examination of the Milky Way Galaxy in the Interplanetary Age revealed several locations where artificial emissions seemed to indicate the existence of advanced civilisations; but these locations were all many tens of thousands of light years away. These civilisations (if real) were so far away they might disappear before any signals reached them. But would there be any closer civilisations that telescopes might not reveal?

Those early Terragens who were expecting a galactic community of civilizations in the region near Sol were disappointed. Space turned out to be empty and desolate, and aliens few and far between. The first remnant of alien technology, the fragmentary hull of a robotic satellite, was found orbiting Epsilon Sculptoris A in 1460 AT. This artifact was 196 million years old, a relic of the unnamed species HIE636MZE.

Although a few of the alien sophont races that have been discovered so far have willingly joined the body of Galactic society, others are aloof or reclusive, lack interest or are unable to understand such concepts. Some, lile the Meistersingers and the Wayfarers, appear to have some measure of contact with the more distant galactic civilisations, but so far they decline to share any significant information concerning these topics.

The most extensive alien empire that has so far been contacted is that of the Muuh; at first believed to be merely a faded remnant of an ancient empire, these slow, low-temperature creatures in fact have a large and widely dispersed network of colonies which are protected by utterly alien AI weapons systems.

Not one single alien race has been found to be similar in physiology to any metazoan life form that originated on Earth, and the process of panspermia has been shown to have had only a minor effect on the emergence of life in the Terragen Sphere. This is not to say that former races did not engage in terraforming and provolve both their own local and other species, for some of them clearly did.

Recent exploration has shown that some xenosophont empires, such as the Tkzeph Empire and the Auld Limners, were much more extensive than had previously been believed. This invites even more the question of how such mighty empires could remain for tens or hundreds of thousands of years, and then suddenly disappear. Speculation ranges from mass transcension to doomsday weapons and mysterious robot warships, and consensus regarding the answer remains elusive.

  • AI, Alien  - Text by Anders Sandberg, amended by Steve Bowers
    There is much speculation, but rather less knowledge, on the psychology of ais from from non-Terragen races extinct or extant.
  • Alien  - Text by M. Alan Kazlev
    Generic term for any non-terragen sapient being. The term xenosophont is also equivalent.
  • Archivists  - Text by Richard Baker
    Vanished builders of certain hi-tech objects.
  • Asoka's Pillar - Text by M. Alan Kazlev
    An alien Dyson sphere outside the galaxy, sending strange signals.
  • Auld Limner  - Text by Peter Kisner, M. Alan Kazlev and Anders Sandberg
    Perseus Arm (and possibly also Outer Arm) space-faring predecessors of the Limners.
  • Batholithic Civilisation, The  - Text by Steve Bowers
    Unnamed species: HIE201NPE
  • Beacon Project, The  - Text by Todd Drashner
    An attempt to contact extragalactic intelligence.
  • Black Acropolis  - Text by Anders Sandberg
    A Dyson swarm built by a vanished civilization that has since been colonised by a number of other species.
  • Chahipho Collection  - Text by Anders Sandberg
    Major art collection in the Vast Endeavour system gathered by the AI godlet Chahipho in the Era of Fragmentation.
  • Chorus  - Text by Stephen Inniss
    Homeworld of the xenosophont provolves the Jade Chime Singers.
  • Daharrans, The  - Text by Anders Sandberg
    A tragic victim of cross-species congress, the Daharrans are a quite humanoid species — at least they breathe a human-breathable oxygen atmosphere and are land-living omnivores from a terrestrial world.
  • Dawn Hunters  - Text by Anders Sandberg and M. Alan Kazlev, with additional suggestions by Steve Bowers.
    Apparently mythical entities from the galaxy's ancient past.
  • Dead Drifter  - Text by James Rogers
    A deceased xenosophont found drifting through space in Sagittarius, during the late First Federation Age, the only recovered specimen of the (presumably) extinct alien species HIE091MZE.
  • Deepwood  - Text by Todd Drashner
    Deep space orwood species of probable alien origin.
  • Doreen/Doreens  - Text by Stephen Inniss, expanded and amended from original material by Anders Sandberg
    Chlorine world, former home of the extinct Doreens.
  • Drake Equation  - Text by M. Alan Kazlev
    An early (pre-interstellar age) attempt to estimate the number of civilizations in the galaxy, according to the statement that the fraction of stars harboring intelligent life equals the number of all stars times a sequence of fractions, such as the fraction of all stars having planets, the fraction of planets that are habitable, and so on.
  • Dyglufsare  - Text by Anders Sandberg
    Marsh dwelling xenosophonts.
  • Energy Emissions and Civilization Types  - Text by Stephen Inniss and Steve Bowers
    A common method for classifying xenosophont civilizations by their energy emissions.
  • Enforcer Objects  - Text by Steve Bowers
    Automatic stealthy weapons left behind by extinct aliens
  • Epsilon Sculptoris  - Text by Steve Bowers
    Binary system 89.5 light years from Sol.
    The first alien artifact, a fragmentary hull of a autonomous vessel, was discovered here in 1460 AT. This artifact was 196 million years old, a relic of the unnamed species HIE636MZE.
  • First Contact  - Text by Steve Bowers
    Strategies and policies for contact with alien life forms (xenobiota) and Xenosophonts (intelligent alien life).
  • Galactic History  - Text by M. Alan Kazlev
    Branch of science and school of philosophy dealing with the history of mindkind in the Galaxy as a whole.
  • Golden Tower Builders, The  - Text by M. Alan Kazlev
    Extragalactic alien civilization known to have built planetary megastructures.
  • Halogenics  - Text by Stephen Inniss
    The Halogenics are a hypothetical clade or group of clades, now believed to be extinct. They seeded a large number of chlorine worlds about 780 million years ago.
  • Hedrile, The  - Text by Loopquanta
    A presumably artificial wormhole of unknown design, origin and destination; it has not yet been traversed successfully.
  • Hildemar's Knots  - Text by Anders Sandberg
    Alien species first discovered in the neutron star KJEI-54-458945 in the Einstein's Revenge Cluster.
  • Hollerith Anomaly Object   - Text by HÃ¥kan Andersson
    A nebula in the Chronos Cluster that contains a nanecology, some semi-sentient entities, and a number of odd phenomena. It is believed to have been left behind by a xenosophont civilization, now no longer evident and assumed by some to have transcended.
  • Hov's'sa  - Text by Aaron Hamilton
    Extinct Aquatic Xenosophonts.
  • Hyraians  - Text by Tsochar, with some additions by Steve Bowers
    An extinct alien race that produced human-like wall paintings.
  • Iahi Daon Empire, The  - Text by Aaron Hamilton, some comments by Steve Bowers
    Xenosophont species extinct for more than 7 million years; known only from remains on the former homeworld and from some massive generation ships.
  • Inhibitor - Text by M. Alan Kazlev
    Hypothetic super-powerful alien race or races proposed to explain why most advanced civilizations fail after only a few tens of thousands to a few millions of years. The Dawn Hunters are the most popular example of inhibitors, although it is not known if they even exist, or if they do, if they really are inhibitors.
  • Ishtar's Necklace  - Text by Liam Jones
    Ancient Xeno Megastructure in the Carina Rush.
  • Jacks, The  - Text by Anders Sandberg; expanded by Stephen Inniss
    The Jacks (officially known as HIE233MPE) are a xenosophont species, or possibly a cluster of related species, named for a toy of ancient human baseline origin called a "Jack-in-a-box". Their name springs from the fact that they are apparently neither extinct nor extant; instead they have "popped up" several times in the past and may or may not return at some point in the future.
  • Jesters, The (HIE156CZE)  - Text by James Rogers
    Extinct alien species known only from ancient Muuh records
  • Kappa Khitai VI-J  - Text by M. Alan Kazlev
    Terraformed by HIE236PPE (extinct xenosophont race).
  • Labyrinth  - Text by Todd Drashner
    Mars like world toward the outer Perseus Arm, known for its alien tunnel complex.
  • Ma-Tesh  - Text by Anders Sandberg
    One of the three forms of written Daharran.
  • Medium Energy Emission Civilisations (MEECs)  - Text by Steve Bowers
    Medium scale civilisations that have been detected in the Milky Way and elsewhere
  • Metric Ghosts  - Text by Todd Drashner
    Unusual, apparently highly mobile, distortions of space-time metric.
  • Miracle City  - Text by Anders Sandberg
    A planet/megastructure constructed by a former xenosophont civilization that is encrusted with fractal buildings that extend far into orbit.
  • Mysterian - Text by M. Alan Kazlev
    The name used by the local populace to describe the long vanished terraformers of alien origin who terraformed Ararat II. The mysterian jungle is made of the numerous plant/jellyfish creatures that have taken residence on the planet and, through accident or not, and outlived the mysterians themselves.
  • Mythical Xenosophonts  - Text by John B with additions by Steve Bowers
    Legends of hidden aliens in the midst of the Orion Arm civilization.
  • Oceanus Ultimata  - Text by Todd Drashner, with some comments by M. Alan Kazlev and Anders Sandberg
    Star in Carina Outer Volumes surrounded by an apparently artificial water ocean-ring.
  • Omicron Hygeras Object, The  - Text by Aaron Hamilton
    Mysterious alien artifact.
  • Porrima  - Text by M. Alan Kazlev
    Twin stars where the first high technology non-Terragen artifact — a derelict alien starship — was discovered in 3752 by the Virginis Combine ship Fra Angelico. The system is currently Solar Dominion protectorate inhabited by a number of bioid and cyborg clades. There is a small but well-equipped Exoarcheology Institute, and a highly accurate reconstruction of the Fra Angelico, along with a superficial reconstruction of the artifact, is a popular tourist attraction.
  • Postalien  - Text by M. Alan Kazlev
    A non-Terragen (alien) who has attained the status of an S1 or higher transapient. Sometimes called a postxenosophont.
  • Rak Mesba  - Text by Radtech497
    A xenosophont megastructure in the form of a circumstellar disc
  • Raksha  - Text by Steve Bowers
    A weird moon with alien ruins
  • Red Globular Galaxies  - Text by Steve Bowers
    Distant galaxies optimised for habitation by xenosophonts.
  • Restorers  - Text by M. Alan Kazlev
    Like the Dawn Hunters, a possibly mythical ancient race.
  • RG Vijayanta III  - Text by M. Alan Kazlev
    Terraformed by HIE236PPE.
  • Search For Non-Terragen Intelligence, The  - Text by Steve Bowers, additions by Stephen Inniss
    A large number of xenosophont civilizations have been detected by their emissions but have not been contacted due to light-speed lags. Some seem to be comparable to the Terragen Sphere in extent.
  • Semblance of Eternity  - Text by Matt, Dagon, and John B
    Disputed alien artifact.
  • Sentients Overview  - Text by M. Alan Kazlev, some additional notes by John B
    A list of life-forms across Known Space.
  • Sextans Swarmers - Text by M. Alan Kazlev
    Nanecology / nanoswarm detected across much of Sextans A (Irregular galaxy - Local Group). Its origin and toposophic nature is unknown. What seem to be a smaller number of similar nanecologies have been detected in Sextans B, showing they were able to make the journey of some million light years separating the two small galaxies.
  • Steelcliff  - Text by Tony Jones
    The first alien BGC system, discovered in 7852.
  • Sundrivers, The  - Text by Todd Drashner
    Alien civilization discovered in the Virgo cluster approximately 60 million ly from the Milky Way. The seem to be involved in a megascale project that involves the movement of entire stars.
  • Tau Felis Minoris II - Text by M. Alan Kazlev
    A cold planet altered by the unnamed species HIE236PPE (an extinct xenosophont race) so that it supports an ecology of cold-adapted lifeforms. These lifeforms share a common ancestry with those found on 12 other worlds.
  • Terraforming Remnants - Text by Anders Sandberg
    Natural and artificial ecospheres left by any of several long-vanished terraformer species known only for the biospheres they left behind long ago. Currently terragenkind is busy terraforming suitable planets in the galaxy, and even if they disappear there are going to be lots of human- and ai- derived biospheres left behind. In a few hundreds of millions of years intelligent life might evolve independently there. This life would find a few other habitable worlds with suspiciously similar biochemistries.
  • Thiogens, The  - Text by Matthew C. Johnson
    Extinct xenosophonts presumed to be responsible for a number of sulphurogenic biospheres on Vitriolic type worlds.
  • Thyresta  - Text by Anders Sandberg
    Extinct alien species, inhabited New Montana (YTS-4885002-3825-IV; MPA).
  • Tkzeph Empire, The  - Text by Aaron Hamilton
    Vast expansionist theocratic/ (?)aicratic starfaring empire that disappeared without a trace some 312 million years ago.
  • Triangulum Transmission, The  - Text by Todd Drashner
    A complex message from another galaxy, giving details of several alien races.
  • Tunh Xenohole, The  - Text by Anders Sandberg, with comments by Steve Bowers.
    System with an alien Wormhole.
  • Ultimates, The  - Text by Anders Sandberg and M. Alan Kazlev
    A static, genetically optimized phylum of sophonts inhabiting the Black Acropolis.
  • Unnamed species HIE300CZE  - Text by Steve Bowers
    Predatory species provolved by the Muuh; hopefully extinct.
  • Unnamed species: HIE072CZE   - Text by Aaron Hamilton
    Species which withdrew from the Orion Arm 5.4 million years ago.
  • Unnamed Species: HIE121CZE   - Text by Aaron Hamilton
    Xenosophonts which vanished 31 million years ago.
  • Unnamed Species: HIE236PPE  - Text by Aaron Hamilton
    Xenosophont species that was capable of interstellar travel, extinct for at least 2 billion years, deduced from the common ethane-based biochemistry of fourteen worlds that are now within the Terragen Sphere.
  • Unnamed Species: HIE565MZE   - Text by Aaron Hamilton
    Xenosophont species known from 125 million year old ruins on a single planet; apparently this species became extinct without developing interstellar travel.
  • Unnamed species: HIE636MZE  - Text by Aaron Hamilton, updated by Steve Bowers
    The first indisputable physical relic of an alien civilisation capable of extraplanetary activity, discovered in orbit around Epsilon Scuptoris A in 1465 AT by a First Federation Exploration mission.
  • Whisper  - Text by Todd Drashner
    Planet covered in a sophont grassland xenoecology, perhaps of artificial origin.
  • World of Meditating Idols  - Text by M. Alan Kazlev
    BD +56°1954 / (774 Sagrei VI) - Inner Sphere Gaian Type world; first planet to be discovered with alien ruins (17th century AT).
  • Xenobiont  - Text by M. Alan Kazlev
    Generic term for alien (non-terragen) lifeform. May be animal-like, plant-like, protistan, exotic chemistry, or any other possibility. Does not have to be sophont. In fact just as on Earth, very few alien species ever evolve any measure of cognitive intelligence.
  • Xenomorph - Text by Steve Bowers
    Any Terragen entity using an artificial alien (xenosophont) body for the purposes of cultural contact, exploration or colonisation.
  • Xenosophont Gallery  - Text by Various Artists
    Images of the various Xenosophonts (Alien Species) in the Orion's Arm Volume
Related Topics
Development Notes
Text by M. Alan Kazlev and Steve Bowers

Initially published on 02 July 2000.