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{{Indicator|featured=true}}

{{Planet infobox
|name = Argolis (Tau Ceti IV)
|image = [[File:TauCetiSurface.png|300px]]
|caption = The surface of Tau Ceti IV viewed from orbit.
|star, position = [[Tau Ceti]], 3rd orbital
|moon(s) =
|diameter = 72,535.7808 km
|gravity = 1.03 g
|daylength =
|yearlength = 642.13700343 days
|atmosphere =
|temperature =
|demonym = New Cascadian
|species = [[Human]]
|population = ''Colony Era'' - ~30,000 <small>(human)</small>
|government = Democratic corporatocracy
}}
{{Quote|Colonizing an exoplanet was never gonna be easy, but Tau Ceti... Maybe it's more than we can handle. Maybe it doesn't want us here.|[[Clarissa Song]]}}

'''Argolis''', most commonly referred to as '''Tau Ceti IV''', is a planet in the [[Tau Ceti]] system, twelve light years away from [[Sol]], and the third planet colonized by humanity.<ref name="CDXexo"/> In [[2787]], [[New Cascadia]] was established by [[Human|humanity]], using the [[UESC Marathon|UESC ''Marathon'']]. Conditions on the planet were initially very hospitable to humans, but after a few months many of its natural systems seemed to collectively turn against the colonists.<ref>''Marathon'' (2026), Codex, Drinkable Cheeseburger: SUBSISTENCE NOTES</ref>

The colony repulsed an attack by the [[Pfhor]] fighter ''[[Sfiera]]'' in [[2794]], but was partially destroyed in a following Pfhor attack that year.<ref>[https://marathon.bungie.org/story/bungie.html ''Marathon'' (1994), The Lost Network Packets]</ref> Further issues from the outbreak of a [[Lore:Novel contagion|novel contagion]] and the eruption of the alien [[Lore:Anomaly|Anomaly]] from beneath the surface of the planet led to the downfall of the colony.<ref name="Mrthn26">''[[Marathon (2026)]]''</ref>

The loss of communications between New Cascadia and the Sol system was realized by the [[UESC]] by [[2795]],<ref>[https://marathon.karnemir.com/marathon/season-0/uesc/memoranda ''Marathon'' (2025) ARG, Memorandum for the Secretary-General Draft A]</ref> and in [[2797]] they sent the [[UESC Equanimity]] under [[Project Goliath]] to investigate the status of the colony.<ref>[https://marathon.karnemir.com/marathon/season-0/uesc/letters ''Marathon'' (2025) ARG, Letter from Bethany R Montenegro-Sankara]</ref> The Equanimity arrived in [[2893]], deploying [[Autonomous Robotic Soldier|ARS]], UESC-aligned forces (including UESC-aligned [[Runners]]), and independent mercenary Runners serving Earth-based [[factions]] to salvage what remained of the colonization effort.<ref name="Mrthn26"/>

== Overview ==
[[File:TauCetiIV Marathon.png|thumb|300px|right|The partially destroyed UESC ''Marathon'' orbiting Tau Ceti IV.]]
=== Astronomical features ===
Tau Ceti IV is the third planet orbiting the star Tau Ceti. Its orbital period is 642.13700343 days. It has an equatorial circumference of 72,535.7808 kilometers, with a mass greater than or equal to 3.93 M•. Its surface gravity was 1.03 g.<ref name="CDXColoniz"/> It orbits within an anomalous gap in the system's debris disk. As a result the planet was at low risk of impact events which posed a risk to civilization at the time of its colonization. When the ''Marathon'' arrived in the system, its environmental satellites detected a likelihood of only two continental impact events within the next century.<ref name="CDXOrbSat">''Marathon'' (2026), Codex, Survey Drone Cartridge: REPORT FROM ORBITAL SATELLITES</ref>

=== Environmental features ===
The surface of Tau Ceti IV was similar to that of Earth, with familiar features like water, plants, animals, Earth-like gravity, and an oxygen-rich atmosphere, all noted as reasons for its colonization.<ref>[https://www.youtube.com/shorts/UNEiwF8ZK48 Exoplanet Colonization | Marathon]</ref> Its surface pressure was 200.6235 KPa at sea level.<ref name="CDXColoniz"/> It had a temperate climate with a humid, warm-summer subtype. Environmental satellites deployed when the ''Marathon'' arrived in the Tau Ceti system detected no high priority mineral resources, no volcanic activity, low risk of droughts, moderate risk of flooding, low risk of extreme weather (with seasonable storms comparable to non-cataclysmic Earth weather).<ref name="CDXOrbSat"/>

==== Locations ====
*[[Lore:New Cascadia|New Cascadia]]
**Colony Farming Sector<ref>''[[Marathon (2026)]]'', [[Codex]], [[Dire Marsh: Initiation]]</ref>
***[[Lore:Dire Marsh|Dire Marsh]]
**Colony Outskirts<ref>''[[Marathon (2026)]]'', [[Codex]], [[Perimeter: Initiation]]</ref>
***[[Lore:Outpost|Outpost]]
***[[Lore:Perimeter|Perimeter]]
**[[Lore:Abyss|Abyss]]<ref name="CDXColony"/>
**[[Lore:Anchor|Anchor]]<ref name="CDXColony"/>
**[[Lore:Hearth|Hearth]]<ref>''[[Marathon (2026)]]'', [[Codex]], [[Welcome Package]], [[WELCOME MESSAGE: STRAUSS]]</ref>
**[[Lore:Javelin|Javelin]]<ref name="CDXColony">''[[Marathon (2026)]]'', [[Codex]], [[UESC Marathon Model]], [[TAU CETI IV COLONIZATION]]</ref>
*Tau Ceti IV low orbit<ref>''[[Marathon (2026)]]'', [[Codex]], [[Cryo Archive: Initiation]]</ref>
**[[UESC Marathon|UESC ''Marathon'']]
***[[Lore:Cryo Archive|Cryo Archive]]

[[File:TauCetiLandscape.png|thumb|right|300px|The [[Dire Marsh]] region of Tau Ceti IV.]]

=== Ecology===
Before [[New Cascadia]] was established, drone operators performed essential ecological surveys of Tau Ceti IV. These surveys showed that, compared to Earth, Tau Ceti IV had relatively low megafauna populations, with little diversity. Early scans showed no land mammals, though a few amphibious specimens resembled [[Wikipedia:Monotreme|monotremes]]. The surveys also showed that the planet had no organisms capable of scavenging human waste or discarded food, and urged for establishing waste treatment facilities to curb the ecological impact of human presence. The release of reanimated specimens from the ''Marathon's'' biostock was prohibited until New Cascadia reached sustainable conditions for megafauna.<ref>''Marathon'' (2026), Codex, Survey Drone Cartridge: ECOLOGICAL BEST PRACTICES</ref>

During colony expansion in [[Lore:Perimeter|Perimeter]], invasive Earth plants were observed growing naturally outside of controlled environments. Some colonists expressed concern about ecosystem disruption, but the representative botanist explained that the [[Exoplanet Seed Vault]] was curated with organisms that were as compatible with Tau Ceti IV as possible, and posed a low risk of displacing native life.<ref>''Marathon'' (2026), Codex, Shrink-Wrapped Bonsai Tree: RECORDED TOWN HALL.</ref>

[[File:Perimeter Screen MicrobialThreats.png|thumb|right|300px|A colony era sign warning about microbial threats.]]
In 2893, [[NuCaloric Agricultural|NuCaloric]] AI [[Gaius]] noted that a [[novel contagion]] present on the planet caused rapid rates of mutation in native organisms, with genomic changes noticeable in months, rather than decades or centuries as observed on Earth. It was further noted that the contagion's effect on Earth organisms was wildly varied.<ref>[https://marathon.karnemir.com/marathon/contracts/nucaloric#h.351a25c5f7p8 ''Marathon'' (2026), Contracts: NuCaloric, Selection Pressures]</ref> After sampling both inert and active samples of the contagion, the AI determined that "mosaic spores", part of the contagion's genomic makeup, were a reproductive vector for at least 4 distinct fungal species native to Tau Ceti IV and allowed transfer of genetic material [[Wikipedia:Horizontal gene transfer|across species]].<ref>''Marathon'' (2026), Codex, Selection Pressures [4/4]: MASS ANALYSIS: NOVEL CONTAGION</ref>

==== Flora ====
The flora of Tau Ceti IV featured a mix of native species, Earth transplants/invasives, and bio-synthetic organisms. These included [[Sparkleaf]], the [[Tarax|Tarax plant]], and [[Poison plant|poison plants]] that exploded in close proximity to Runners, releasing a toxic cloud.

During the Colony Era, toxic pollen regularly accumulated on the blades of [[TOI AP Flex V7]] drones doing low-altitude sweeps over potential agricultural sites.<ref>''Marathon'' (2026), Codex, Survey Drone Cartridge: DRONE MODIFICATIONS</ref>. Vehicles left outside near [[Lore:Perimeter|Perimeter]] quickly had their engine compartments infested with mold from airborne spores, affecting both mechanical and electrical systems in the vehicles.<ref>''Marathon'' (2026), Codex, Grievance Log Record: GRIEVANCE: STAFF HAZARDS</ref>

A local species of [[Shrink-Wrapped Bonsai Tree|bonsai-like tree]] was genetically modified to be easier to care for and given to colonists as a morale-boosting initiative. A tea brewed from its leaves was said to have effects similar to caffeine.<ref>''Marathon'' (2026), Codex, Shrink-Wrapped Bonsai Tree: BONSAI CARE SHEET</ref>

Other recorded species included yellow-pink flowers with gills which could be used to sweeten dishes, yellow fungi which caused hallucinations after 5-9 days of consumption, [[flatberries]] which grew under tree roots and could be used for hydration, and [[bitterstars]] which could be used as a stimulant.<ref name="CDXPostApocFood">''Marathon'' (2026), Codex, Anchorite Provisions: FOOD PROCUREMENT</ref>
<gallery>
File:TauCetiTaroPlant.png|A plant species similar to [[Wikipedia:Taro|Taro]] found in [[Dire Marsh]].
File:Perimeter Sparkleaf.png|[[Sparkleaf]]
File:DireMarsh Tarax2.png|[[Tarax]]
File:Loot Shrink-WrappedBonsaiTree.png|A [[Shrink-wrapped bonsai tree|shrink-wrapped bonsai tree]].
File:ToxinHazardPlant.png|A [[Poison plant|poison plant]] with similar nodules to those found on [[Tick]] nests.
File:Triage PlantToxin.png|A [[Triage]] shell suffering the effects of the poison plant.
</gallery>

==== Fauna ====
The planet's fauna included a species of mega-arthropod, the [[tick]], many birds, including the vulture-like [[skrac]] and small flocking birds, monotremes such as a [[six-legged mole]], amphibians such as frogs, and plentiful arthropods, such as the [[astacid]], [[giant hissing beetles]], dragonflies, and many species of [[Wikipedia:Lepidoptera|Lepidoptera]].<ref name="CDXPostApocFood/> Agricultural water filters were sometimes clogged by nesting [[filament worms]], which were impossible to eradicate using pesticides, targeted genome disruption, or nanotech.<ref>''Marathon'' (2026), Codex, Data Reconstruction [1/3]: AGRICULTURAL INSPECTION</ref> Other species included the [[Wikipedia:Oviparity|oviparous]] [[scaledove]]<ref name="CDXPostApocFood/> and organisms known as [[chockisens]], which occasionally harassed [[New Cascadia]] colonists.<ref name="manual">[https://marathon.bungie.org/story/_files/Marathon_Manual.pdf ''Marathon'' (1994), Marathon Manual, page 6]</ref>
<gallery>
File:Tick.jpg|[[Tick]]
File:TauCetiVulture.png|[[Skrac]]
File:DireMarshCrayfish.jpg|[[Astacid]]
File:TauCetiDragonfly.jpg|Dragonfly
File:2026 Marathon Thief Vignette Press Kit COMPRESSED 13.jpg|Butterflies
File:Perimeter Flock.png|Small birds
</gallery>

== History ==
{{Quote|Everything was fine just a few months ago, and now it's like everything here's trying to kill us.|Post-colony survivor}}<ref>''Marathon'' (2026), Codex, Drinkable Cheeseburger: SUBSISTENCE NOTES</ref>
[[File:Marathon EarthDeparture.png|thumb|right|300px|The ''Marathon'' departs [[Earth]] for Tau Ceti.]]
=== Pre-Expedition ===
During exoplanet candidate selection for the [[UESC Marathon|''Marathon'']] expedition, a joint panel of [[UESC]] physicists and [[NuCaloric Agricultural|NuCaloric]] agronomist observed that Tau Ceti IV met habitability criteria in at least one major landmass, had atmospheric readings that showed abundant carbon-based plant life, and likely required no long-term terraforming to be agriculturally self-sustaining. It was for these reasons that the planet was approved as the target candidate.<ref name="CDXexo">''Marathon'' (2026), Codex, Survey Drone Cartridge: EXOPLANET CANDIDATES</ref>

=== Colony Era ===
{{stub|section=yes}}
==== Arrival ====
In [[2773]] the [[UESC Marathon|UESC ''Marathon'']] arrived in the Tau Ceti system and began colonization efforts on the planet.<ref name="Lostpacket">[https://marathon.bungie.org/story/bungie.html ''Marathon'': the Lost Network Packets]</ref> Specialists were the first people woken from cryo, before civilian colonists, based on immediate needs.<ref>''Marathon'' (2026), Codex, Survey Drone Cartridge: EARLY SURVEY WORK</ref> 

By [[2775]], the ''Marathon'' had completed two years of orbital study of Tau Ceti IV, mapping its weather, seasons, tides, and local environments to select the best colonization sites.<ref name="CDXMrthnMssn">''[[Marathon (2026)]]'', [[Codex]], [[UESC Marathon Model]], [[UESC MARATHON MISSION]]</ref> During this two year period, probes were launched to gather soil, water, and air samples, as well as flora, fauna, and mineral samples. After this two year period, the ''Marathon'', with the aid of [[Arthur]], was locked into a geosynchronous orbit above the chosen colony site. Automated pre-fabricated structures were deployed to the surface, mapping potential farmlands, identifying sources of essential resources, and damming or deepening rivers based on the needs of the soon-to-be-established colony.<ref name="CDXColoniz">''[[Marathon (2026)]]'', [[Codex]], [[UESC Marathon Model]], [[TAU CETI IV COLONIZATION]]</ref>

[[Bastion]] was the first AI deployed to the planet's surface at [[Lore:Javelin|Javelin]], "the seed from which the rest of the colony will grow". [[Darius]] and [[Naraah]] were then relocated to [[Lore:Anchor|Anchor]] and [[Lore:Abyss|Abyss]]. [[Arthur]] and [[Gabriel]] were then transferred to [[Lore:Hearth|Hearth]], which would become the Central Living Complex. [[Lilith]] and [[Joy]] remained aboard the ''Marathon'' to assist with colonist wake cycling over a period of many years.<ref name="CDXColoniz"/>

In [[2777]], the first wave of citizen colonists were awakened from cryo to begin study and preparation for colonization efforts.<ref name="CDXColoniz"/>

In [[2779]], the first wave of colonists arrived planetside.<ref name="CDXColoniz"/> ''Marathon'' scientists were amazed to find clean water, flourishing plants, and fearless animals—a garden world with more than ideal conditions for human habitation.<ref>''Marathon'' (2026), Codex, History for Young Readers: OUR COSMIC HOME</ref> Dr. [[Clarissa Song]] was one of the first colonists to step foot in [[Dire Marsh]].<ref>''Marathon'' (2026), Codex, Selection Pressure [4/4]: FIELDWORK REQUEST: C. SONG</ref>

By [[2787]], [[New Cascadia]] had been formally established.<ref name="Lostpacket">[https://marathon.bungie.org/story/bungie.html ''Marathon'': the Lost Network Packets]</ref>

[[File:UESCMarathon OrbitalBombardment.png|thumb|right|300px|Colonists witness the ''Marathon'' come under attack from the second wave.]]

==== Contact event ====
In [[2794]], the ''Marathon'' came under attack by elements of the [[Pfhor|Pfhor Empire]]. The initial attack was repulsed by ten Battleroids implied to be hidden by MIDA, but later both the ''Marathon'' and [[New Cascadia]] would be subjected to heavy orbital bombardment in what would come to be known as the [[contact event]].<ref>''Marathon'' (2026), Codex, Class B Anomalous Material: UESC INTERROGATION: ALVA, T.</ref>

==== Novel contagion ====
In [[2812]]<ref name="cinematic">[https://www.youtube.com/watch?v=fvbEnWLRo1s Marathon | Reveal Cinematic Short]</ref> a [[Novel contagion|novel contagion]] appeared in colony bio-research and food facilities, particularly algae ponds used for protein cultivation, before spreading to other facilities.<ref>''Marathon'' (2026), Codex, Data Reconstruction [1/3]: AGRICULTURAL INSPECTION</ref> It eventually infected colonists, causing illness and death.<ref name="cinematic"/>

==== The Anomaly ====
In [[2827]]<ref name="cinematic"/> the [[The Anomaly|Anomaly]] erupted from the surface of the planet, causing significant disruption to colonization efforts due to its unpredictable effects on physics, biology, and technology (including AI systems).

=== Post-Colony Era ===
==== Runner Operations ====
{{stub|section=yes}}

== Production notes ==
* Tau Ceti IV has a real-life counterpart in the Tau Ceti system, as two super-Earths were detected in 2017 that are located in the inner and outer edges of the system's habitable zone.<ref>[https://iopscience.iop.org/article/10.3847/1538-3881/aa83b4#artAbst "Color Difference Makes a Difference: Four Planet Candidates around τ Ceti." F. Feng ''et al'' 2017 ''AJ'' 154 135]</ref>

== Gallery ==
<gallery>
File:TauCetiSystem.png|A digital render of the Tau Ceti system.
File:TCIV Graphic.png|A digital close-up of Tau Ceti IV.
File:TauCetiHurricane.png|A hurricane raging across the surface of Tau Ceti IV.
File:TauCetiSurface2.png|Another view of Tau Ceti IV's surface, including floodplains.
File:7.3.2794.png|The date shown in the [https://www.youtube.com/watch?v=fvbEnWLRo1s Reveal Cinematic Short] when the attack on the ''Marathon'' is depicted.
File:3.13.2812.png|The date shown in the Cinematic Short when the [[Novel contagion|novel contagion]] is depicted.
File:12.21.2827.png|The date shown in the Cinematic Short when the [[The Anomaly]] is depicted.
File:TauCetiDesert.png|A desert on Tau Ceti IV.
File:TauCetiArid.png|Runners traversing an arid region of Tau Ceti IV.
File:TauCetiField.png|A field on Tau Ceti IV.
File:TauCetiMarsh.png|[[Dire Marsh]], a [[zone]] on Tau Ceti IV.
File:DireMarsh Wilderness.png|The wilderness outside Dire Marsh.
File:TauCetiFlora.png|The dense flora of Dire Marsh.
File:NewCascadiaMountains.png|A mountain range near [[Lore:Perimeter|Perimeter]] on Tau Ceti IV.
File:TauCetiNight.png|Dire Marsh at night.
</gallery>

=== Classic ===
<gallery>
File:M1 Pfhor Chapter Image.gif|The ''[[Sfiera]]'' destroying the shuttle ''[[Mirata]]'' in orbit around Tau Ceti IV during the [[contact event]], from ''[[Marathon (1994)]]''.
File:M2.01.1.2.1.gif|Tau Ceti IV displayed alongside the other main planets in the franchise, from ''[[Marathon 2: Durandal]]''.
</gallery>

=== Concept Art ===
<gallery>
File:TauCetiImage.jpg|Early concept art of Tau Ceti IV.
File:ViDoc1 TauCetiConcept.png|Another early concept of Tau Ceti IV.
File:ViDoc1 RunnerConcept5.png|Concept art of a dead Runner and a Tau Ceti insect.
</gallery>

==List of appearances==
{{stub|section=yes}}
*''[[Marathon (1994)]]'' {{1st}}
*''[[Marathon (2026)]]''

==References==
<references/>

[[Category:Planets]]
[[Category:New locations]]
[[Category:ARG content]]