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Arin was a human core planet that once served as a great center of political influence, economic development, and military strength. Before being abandoned, it was of critical and strategic importance for humanity and their survival. As a core planet, Arin provided significant financial, material, and other resources to AE and the Knight Order in exchange for exemption from mandatory military conscription. Despite this however, many Arin soldiers are found throughout the universe as the planet's self-defense force, the AUA, still voluntarily deploys expeditions to the vulnerable frontiers of the Absolute Defense Line.

Arin was different from other core planets in that it was de facto seen as the capital of humanity since it hosted the Central Order Supreme Headquarters of the Knights. Given its power and wealth, it was presumed that Arin's scope was very broad and far-reaching. Besides Planet Arin itself, the term Arin, as a polity, encompasses several nearby colonies orbiting the planet (such as the 7th Colony of Arin) and other celestial bodies within the same galactic system.

The episodes of Knight Run are either set in Arin or are highly influenced by the events that occurred from it. As such, the planet is a central setting for the whole series. Main Episode-0 Pray covers the War of Prayer which saw the fall of Arin and the struggle to retake it from Beast Queen E-34. Ultimately however, humanity had to give up Arin due to irreversible erosion and collateral damages from the war which changed the planet's landscape and ecosystem, rendering it inhospitable and unable to support human habitability.


Great WarEdit

Main article: Great War

Arin was a mere frontier planet during the Great War with a small human colony residing on it. Not much is known of Arin until the arrival of the humanitarian aid organization, PF, in CC 230. They established their presence on the planet and significantly brought development with them. When PF transitioned into the Knight Order, they converted Arin into a fortress-planet. The Great War-era Avalon was installed as the foundation of the Knight Order's headquarters, Core Temple. The first generation of Knights were recruited and trained in Arin which would later become an established tradition among the Knightage.

First Battle of ArinEdit

Main article: First Battle of Arin

The militarization of PF necessitated further growth and development of Arin which was done with full support from Knight Order's benefactors: the Leonhard Family, Zail Family, and Ruin Corp. Unfortunately, this also attracted the attention of the Beasts who launched a full-scale invasion of the planet. The Knights valiantly defended Arin and their nascent organization. Eventually, the Knights won the battle and marked the first decisive human victory in the history of the Human-Beast conflict. The Knight Order proved themselves as an extremely competent and effective special forces specializing in anti-Beasts warfare.

War of PrayerEdit

Main article: War of Prayer

Second Battle of ArinEdit

Main article: Second Battle of Arin

Third Battle of ArinEdit

Main article: Third Battle of Arin



The Arin Government is a unified planetary-wide polity that had extended its political reach within its solar/star system. It is a member of the AE alliance but traditionally maintains a broad autonomy from the AE unified structure. It was implied that the Arin Government and the central AE Government both keep a neutral but wary stance with each other due to conflicts in jurisdiction - it also does not help that Arin formulates its own foreign policy and has friendly, close ties with the Knight Order. The Arin Government, while not truly independent, was influential enough to be considered as primus inter pares among other planetary governments and members of AE.


Arin maintains a highly disciplined, experienced, and modern self-defense force known as the AUA. It is an extremely distinguished and reputable military force due to having a powerful potency that could even rival AE. It was implied that, before the fall of Arin, the AUA was the largest armed force there is, second only to the main unified force of the AE alliance. The AUA was very active in participating in the Human-Beast conflict. It routinely sent expedition forces to the frontiers to provide auxiliary reinforcements to conflict zones and other battles against Beasts.

After the fall of Arin, the AUA was split between the home forces who were stuck waging a guerrilla-based survival on the surface, and the expeditionary forces who were recalled from the frontier expeditions. The AUA expeditionary forces regrouped in Planet Valtia for a rescue attempt of their planet and their people. They successfully launched their relief mission but not before clashing against New Alliance command. Once reunited, the AUA spearheaded the Arin Recovery Campaign; their participation was substantial in bringing down the Beast blockade and saturating the plants on the ground which led to the overall victory. When the decision to abandon Arin was finalized, the AUA soon disbanded afterwards.

The AUA was equipped with the latest military technology and tactics. They were further supported by an expansive indigenous defense industry (among which was the PPP Foundation). The AUA boasts itself for adopting several weapon systems in advance such as: the Dolores Armor Suit, the Alcyone design family of warship models, the Arc Rider, AF-1003, YF-1035, TAT-210, Cherry dogs, and other weapons. Both humans and dolls are accepted into service with no discrimination between them. Additionally, many Knights hope to be assigned or attached to the AUA due to its generous compensation and benefits scheme. There are also several platoons of enhanced special forces units that were active in the AUA such as the Kerberos.

Notable InhabitantsEdit


The Knights settled in Arin when Mother Knight, with close assistance from the Zail Family and Leonhard Family, restructured the humanitarian aid support/anti-Beast R&D organization "PF" to the independent paramilitary group known as "Knight Order". Eventually, the Knight Order decided to expand their structure upon gaining official recognition and support from AE. The Northern, Eastern, Western, and Southern Orders were established as branches of the main Central Order that remained in Arin as the overall supreme command and headquarters of the Knights.

The Knight Order academy, known as Knights Training Organization, was staffed and handled by Central Order. This made Arin the main recruitment and evaluation site for prospective Knight trainees.

Zail FamilyEdit

Fleeing the disastrous collapse of their empire during the Great War, the Zail Family made Arin their second home and new base of power after co-founding the Knight Order alongside Mother Knight and the Leonhard Family. It is implied that the Zail Family has substantial influence on the Arin Government and Knight Order. The Zails also have direct ownership and control over huge swaths of Arin's territory while maintaining their own personal army and navy.

Notable LocationsEdit

Core TempleEdit

Space ElevatorEdit

Zail Seabed BaseEdit

Polar RegionEdit

Newta DesertEdit