You step into this era of war as a single Gunbat. You can customize your machine as you like and fight. You are free to accept requests. You are free to be hired by corporations. You are free to cooperate with AMSAS or live as an independent mercenary. But no matter what path you choose, you will eventually encounter them. —The five ghosts who changed Martian history.

Atlas Palesia, a group of emerging cities in the Martian southern hemisphere. It was the front line of resource development and Mars' largest battlefield where corporations, the military, environmental armed organizations, and Gunbats (mercenaries) from around the world gathered. Valendrance Corp, a B-Ghouk member, sought resources; the environmental armed organization CoN took up arms to stop development; and the AMSAS Frontier Expeditionary Battalion intervened under the guise of maintaining order. Everyone fought for their own justice and profit, and the proxy war with no end in sight grew more intense. However, that balance collapsed with a single incident. A total war over the giant oil mining base Armline. Five CH units suddenly appeared on that battlefield. They struck the Corporate forces, they struck AMSAS, and they struck CoN. Ignoring even the concept of friend or foe, they rewrote the battlefield itself with overwhelming combat power, finally destroying Armline. This was the Armline Incident, which remains in Martian history. Following this incident, one name became known throughout Mars. The Spriggans. Oberon 1. Undine 2. Gremlin 3. Pixie 4. Cait Sith 5. Identity unknown. Purpose unknown. Affiliation unknown. A mysterious armed group that repels armies, sinks fleets, and dominates battlefields with just a few members. Are they terrorists, heroes, or beings with some other purpose? No one knows the answer. Eventually, every faction on Mars begins to pursue them. Some to subjugate them. Some to utilize them. And some to reach the "truth" that lies beyond them. This is the beginning of the 'Spriggan Incident,' which would later greatly shake Martian history.

Atlas Palesia: A group of new cities built inside a giant crater in the Martian southern hemisphere. It underwent rapid development triggered by the discovery of large-scale mineral resources sleeping underground, becoming a center for mining, refining, and logistics. Corporations, the military, environmental armed organizations, and mercenaries fight over its enormous interests, leading it to be called "Mars' largest powder keg."

Valendrance Corp: A republican land development corporate community belonging to the B-Ghouk Corporate Alliance. It is a giant corporation leading the urban and resource development of Atlas Palesia, operating numerous private armies and Gunbats to protect its vast interests. Among the development-oriented companies in the alliance, it possesses particularly strong military power and political influence.

CoN: An environmental armed organization advocating for the preservation of the Martian natural environment and underground primitive micro-ecosystems. They engage in radical resistance activities, including sabotage and the use of force, against the disorderly urban and resource development by corporations, and are regarded as a terrorist organization by other factions. On the other hand, many sympathize with their ideology.

AMSAS Frontier Expeditionary Battalion: An expeditionary force dispatched to Atlas Palesia by the AMSAS Central Administrative Committee. While active under the pretext of maintaining public order in frontier regions and protecting AMSAS interests, they actually intervene militarily against corporate forces and armed organizations. Comprising CH units, land combat units, and fleet forces, they are the largest regular military force in the region.

Spriggans: A mysterious elite armed group. They are shrouded in mystery. Their actions lack consistency in terms of factional interests, and they are sometimes viewed as neutral, indiscriminate terrorists.