Xen

{{Article|hl1}}
{{Cleanup}}
{{Spoiler}}
{{Youmayd|the borderworld|the ''Half-Life'' chapter|Half-Life storyline (chapter)}}
{{Location Infobox
|image=FileXen first island.jpg|250px
|name=Xen
|hidei=
|constructed=
|destroyed=
|location=N/A
|builder=
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|era=Black Mesa Incident
|affiliation=Xen
|maps=*c4a1 to c5a1 (HL - ''Xen'' to ''Endgame'')
*of3a2 to of6a5 (Op4 - ''We Are Not Alone'' to ''Worlds Collide'')
*of7a0 (Op4 - ''Conclusion'')
*ba_xen1 to ba_xen6 (BS - ''Focal Point'')
*ba_outro (BS - ''Deliverance'')
*ht99alien (HLD - ''Xen Attacks'')
|designer=*Brett Johnsonhttp//www.brett3d.com/ld_fps.html ''Half-Life'' section on Brett Johnson's official website (mapping)
*Karen Laurhttp//www.norsecode.com/klaur/hl/default.htm ''Half-Life'' section on Karen Laur's official website (textures)
|hidei=
|hideu=
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}}

{{Quote|The borderworld, Xen, is in our control, for the time being... thanks to you.|The G-Man|Half-Life}}

'''Xen''' (pronounced "WikipediaNATO phonetic alphabet|zen" ''Half-Life'' - Lambda Core), or the '''Borderworld''', is a plane of existence connecting two or more dimensions.  It was discovered by Black Mesa research scientists, who regularly traveled there via teleportation to collect samples and study the myriad species of flora and fauna within, despite the extremely high risk of doing so. 

It is the final retreat of Nihilanth's race, and a place where most of the alien species appearing in the Half-Life universe|''Half-Life'' series migrated to before coming to Earth during the Resonance Cascade.

==Overview==
FileXen islands 1.jpg|thumb|left|200px|The first island to be seen by Freeman.
 
Rather than being a planet or an artificial structure such as a space station, all of the locations of Xen visited by the player during the course of the ''Half-Life'' series are on the surfaces of (or within) asteroid-like "islands" floating within a nebular void. 

FileXen first teleport1.jpg|200px|thumb|An example of the organic-looking asteroid cavern-like areas explored on Xen.

Xen is notable for having greatly reduced gravity compared to Earth's; however, given that Xen is composed of low mass asteroids, it is surprising that there is any appreciable gravitational pull at all, let alone a pull strong enough to retain the breathable atmosphere encountered there. It is possible that, given that Xen resides in another dimension or universe, the entire void contains a breathable atmosphere. 

Another feature is that gravity is always directed downwards, rather than towards the asteroids, so that one can actually fall off an asteroid into the void below.

Light behaves oddly in Xen. Looking at the different skybox textures, there are multiple sources for light in the borderworld, either through glowing butts of gas or (in some cases) what seems to be a star or some other stellar body.

The exact fate of Xen after the death of the Nihilanth in ''Half-Life'' is unknown. In ''Half-Life 2'', resistance Teleportation|teleporters are dependent on Xen for intra-dimensional transportation, since the matter stream utilizes the Borderworld as a slingshot to teleport into local space. The The G-Man|G-Man also stated at the end of ''Half-Life'' that he and his "employers" are in control of Xen after the defeat of the Nihilanth. While the G-Man says this, dead Hazardous Environment Combat Unit|Marines, a destroyed tank, and a downed fighter jet can be seen, implying that American military forces have failed at their mission.

===Ecosystem===
The Xen asteroids are home to a wide variety of flora and fauna, forming a complex ecosystem. Although resident in Xen at the time of ''Half-Life'', all of these species originated elsewhere and were forced to flee there to escape attack from their enemies.http//planethalflife.gamespy.com/View.php?view=Mailbag.Detail&id=5 Marc Laidlaw e-mail about Xen on Planet Half-Life Mailbaghttp//www.halflife2.net/forums/showpost.php?p=1994259&postcount=847 Marc Laidlaw e-mail about Alien Controllers on Halflife2.net Forums While mostly seen as lifeless, the presence of water (reddish-green in color) indicates that the dimension is capable of supporting life. 

FileGonarch first.jpg|thumb|left|200px| The Gonarch is one of the largest creatures to be found on Xen.

Some species, such as Barnacles, Bullsquid, Headcrabs, and Houndeyes appear to occupy niches similar to various carnivorous terrestrial animals (albeit with unusual anatomical or physiological features). However, even these creatures are dwarfed by the towering six meter high, four-legged invertebrate known as the Gonarch, which appears to be the final stage of a Headcrab's life cycle.

FileBoids Xen.jpg|thumb|right|200px|Boids glide gracefully through the skies of Xen.

Seen frequently in Xen (and occasionally in Black Mesa, where they transport Alien Grunts), Alien Aircraft glide seemingly without effort through the void. It is uncertain whether these ray-like beings are living creatures or examples of war machines built around advanced biotechnology (such as those used by the Combine). In the closing sequence of ''Half-Life'', and in several areas of ''Blue Shift'', Boids can be seen flying in flocks, emitting resonant calls.

The intelligent species of Xen, such as the Alien Controllers and Vortigaunts, form part of an advanced alien civilization, with species like the Alien Grunts and Gargantua, composing their military. As the player progresses through ''Half-Life'', it becomes clear that this civilization is controlled by a central intelligence, the Nihilanth. Although differing in many ways, the Controllers, Vortigaunts, Grunts, and the Nihilanth share a common morphology that includes a vestigial third limb in the middle of the thorax, suggesting that they are all closely related.

FileXen trees sun.jpg|thumb|left|200px|These Xen Tree|tree-like organisms can be found throughout Xen.

A few creatures that appear in Xen are difficult to categorize as either WikipediaFauna|fauna or WikipediaFlora|flora due to their unusual appearance. Stationary Light Stalk|bio-luminescent stalks appear in large numbers throughout Xen and will retract when approached. The much larger and extremely aggressive (but rarely encountered) Tentacles pose a major hazard to those who wander near their pits. There are also bizarre tree-like structures dotted around the landscape, which may be juvenile or even a separate species of tentacle. The "trees" sway gently and appear harmless when observed from a distance, but stab viciously at any creature that enters their immediate vicinity. There are also strange trampoline-like plants seen in Black Mesa and Xen that release a blast of air when stepped on. A similar kind was seen on Xen which opens and closes, releasing a gust of air like a vent.

===Colonization and civilization===
Since the Combine's takeover of the Xen residents' former world, they retreated to Xen via teleportation and colonized Xen with their buildings and technology (also bringing with them invasive wild-life and pests). The buildings for the Vortigaunts were primitive and lacked luxury or necessary needs of survival (besides the healing pool in the back) due to their social class as slaves. The Vortigaunt's buildings look like small hills carved by an unknown tool.

The military castes live in an industrialized, floral Xen Base. The Nihilanth has its own personal chamber which is heavily defended by Vortigaunts, and Alien Controllers.

==Behind the scenes==
*The "WikipediaNATO phonetic alphabet|zen" pronunciation of the name is given in ''Half-Life''. First by the "shotgun scientist" met in Level A of the Lambda Reactor Core in the Lambda Complex, then by the G-Man at the end of the game, and by Alyx Vance in ''Half Life 2'' chapter ''Entanglement''.

*"Xen 2" is mentioned as an item cut from ''Half-Life 2'' on a board at Valve's headquarters seen in early 2004. It is unknown if it is related to Xen, or another borderworld like Xen, or a direct or indirect reference to Xen.

*The term "Xen" is seemingly related to the Greek term "WikipediaXenos (Greek)|Xenos" (ξένος), translated most of the time as "foreigner", "stranger", or "alien". "WikipediaXenophobia|Xenophobia" is the most common term stemming from it. Furthermore, the WAD file containing the Xen textures (and most of the textures themselves) in the ''Half-Life'' game files is named "xeno.wad".

==Trivia==
*Near the chapter "DARK ENERGY", in the chapter "OUR BENEFACTORS", in the carrier sequence, near the last upwards (with the first view of the full City 17) scene, you can see an unknown alien never seen on the other episodes or even Half-Life 1. That model is only used that time.
*In a brief sequence near the end of ''Half-Life 2'', Wallace Breen|Doctor Breen can be overheard describing "worlds stretched thin across the membrane where dimensions intersect" or "Gas giants inhabited by vast meteorological intelligences." It is likely that Xen is one of the worlds Breen describes here, or even the "membrane".
*It seems that Xen's atmosphere is not dissimilar to that of Earth's, as the Xen wildlife appears to have no trouble surviving on Earth.
*There is in fact one living scientist in the Nihilanth "side" chambers, he can be found sitting on a small ledge in the room with the Gargantua.
*It is a common misconception that many of the creatures seen in the Half-Life universe|''Half-Life'' series originate from Xen. This is actually untrue, as all of the Nihilanth's race retreated there in the stead of a Combine invasion on their own planet.
*In the http//en.wikipedia.org/wiki/Doom_(video_game) Doom mod Massmouth (as well as its sequel Massmouth 2), there is a chart with a list of names of people and planets they were sent to. One of the rows says "Freeman" and the planet "Xen".

==Gallery==
===Concept art===

FileXen view.jpg|View of Xen, with two cut creatures, the Flocking Floater and the Kingpin.
FileXen vista full.jpg|View of Xen, with different creatures, notably the cut Stukabat.
FileInterloper concept.jpg|Concept art for a map of the ''Half-Life'' chapter ''Interloper''.
FileBigmomma concept.jpg|Concept for the ''Half-Life'' chapter ''Gonarch's Lair''.


===On Xen===

FileXen D1 ordering.jpg|Early screenshot.
FileBullsquids drinking on Xen.jpg|Bullsquids seen drinking from a pool.
FileFungus on Xen.jpg|Xen Fungi and a Light Stalk, parts of the Xenian plant life.
FileAlien grunt factory first.jpg
FileTeleport Nihilanth.jpg
FileBullsquid Xen Op4.jpg|Bullsquid drinking.
FileOf bullsquid pond.jpg|Ditto, wide-shot.
FileDy alien0002.jpg|Fungi surrounding a pool on an enclosed island.
FileOf4a xen displacer1.jpg|Mysterious floating islands seen throughout Xen.
FileOf4a xen displacer2.jpg|Ditto, close-up.
FileScientist hanging displacer.jpg|Scientist who came to Xen with another Displacer, clinging to the edge of an island.
FileFocal Point.jpg
FileBa xen50003.jpg|Equipment brought to Xen by Black Mesa.
FileBa xen50005.jpg|Ditto.
FileBa xen50009.jpg|Large Xen crystals making up the Xenian "focal point."
FileBa xen50001.jpg|Survey team equipment on Xen.
FileBa xen50002.jpg|Ditto, with Xen crystal|crystal being studied.
FileCrystal crate.jpg|Xen crystals in a crate on Xen.
FileBa xen60003.jpg
Filess.png|The "Secret Scientist" that can be found in one of the chambers the Nihilanth can teleport Gordon to.


===Xen creatures===
====Cut====

FileArcher model.jpg|The Archer.
FileCharger model front.jpg|The Charger (Xen creature)|Charger.
FileChumtoad model.jpg|The Chumtoad.
FileFast Walker.jpg|The Fast Walker.
FileFlocking Floater model.jpg|The Flocking Floater.
FileKingpin-model.jpg|The Kingpin.
FileMr Friendly model.jpg|The Mr. Friendly.
FileRed Panther Eye model.jpg|The Panther Eye.
FileSand Barnacle model.jpg|The Sand Barnacle.
FileSnapbug model.jpg|The Snapbug.
FileStukabat model.jpg|The Stukabat.
FileSphere open.jpg|Unknown creature / weapon, named "sphere.mdl". It is made of some sort of cannon hidden in a sphere.


====Retail====

FileManta ray double.jpg|The Alien Aircraft.
FileAlien Controller2.jpg|The Alien Controller.
FileAlien Grunt.jpg|The Alien Grunt.
FileBarnacle HL1.jpg|The Barnacle.
FileBoid hl.jpg|The Boid.
FileBullsquid hl1.jpg|The Bullsquid.
FileXen fungus model.jpg|The Xen Fungus|Fungus.
FileGargantua.jpg|The Gargantua.
FileGonarch model.jpg|The Gonarch.
FileHeadcrab model.jpg|The Headcrab.
FileHoundeye.jpg|The Houndeye.
FileIchthyosaur hl1.jpg|The Ichthyosaur.
FileLeech HL1.jpg|The Leech.
FileLight_stalk_model.jpg|The Light Stalk.
FileNihilanth model.jpg|Nihilanth.
FileProtozoa model.jpg|The Protozoan.
FileSnark w.jpg|The Snark.
FileTentacle.jpg|The Tentacle.
FileXen tree.jpg|The Xen Tree|Tree.
FileAlien Slave.jpg|The Vortigaunt.


====Half-Life 2====

FileBarnacle Ep2.jpg|The Barnacle.
FileBullsquid beta.jpg|The Beta Bullsquid.
FileLamarr.jpg|Lamarr, Dr. Kleiner's pet Headcrab. 
FileHeadcrab Standard.jpg|The Standard Headcrab.
FileHeadcrab Fast.jpg|The Fast Headcrab.
FileHeadcrab poison.jpg|The Poison Headcrab.
FileIchthyosaur.jpg|The Ichthyosaur.
FileLeech HL2.jpg|The Leech.
FileVort HL2.jpg|The Vortigaunt.
FileVort Ep2.jpg|Ditto, Source 2007 version.
FileVort slave HL2.jpg|Slave Vortigaunt.
FileVort Ep2 slave.jpg|Ditto, Source 2007 version.
FileUriah model.jpg|Uriah's model


==List of appearances==
*''Half-Life'' {{1st}}
*''Half-Life Opposing Force''
*''Half-Life Blue Shift''
*''Half-Life Decay''
*''Half-Life 2'' {{Mo}}
*''Half-Life 2 Raising the Bar''
*Source Particle Benchmark {{Gf}} {{Nc}}
*''Portal'' {{Gf}} {{Nc}}
*''Half-Life 2 Episode Two'' {{Gf}}

==References==
{{Imagecat|Xen images}}
{{Reflist}}

{{succession
|title=''Half-Life'' story arc journey
|before=Sector F Lambda Complex
|after=Unknown
}}
{{succession
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|before=Sector F Lambda Complex
|after=Sector E Biodome Complex
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{{succession
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|after=Section A-17 Prototype Labs
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{{succession
|title=''Half-Life Decay'' story arc journey
|before=Gamma Labs
|after=Sector E Biodome Complex Transport|Sector E Materials Transport
}}
{{Locations}}
{{Xen}}
CategoryFactions
CategoryWorlds
CategoryXen
CategoryHalf-Life
CategoryHalf-Life Opposing Force
CategoryHalf-Life Blue Shift
CategoryLocations
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