Time flowed like a river, and history surged ever onward.
Five hundred years ago, from Federation Calendar Year 196 to 216, was the era of fiercest conflict between Terra's inhabitants and the interstellar peoples since the Unification War.
The Century Rebellion, which took place during the final decade of the second century, lasted for quite some time. Together with numerous wars including the Frostbearer Campaign, it became collectively known in history as the Twenty Years' War.
Beginning with the Valentine's Day Conflict—Terra Valentine's Day fell on December 12—the Terra Federation, the Lunar City Alliance, and the Cosmic City-State League came into friction during military exercises. That friction swiftly escalated into conflict and even war. Within a single year, all three sides had entered a state of total war, each accusing the others of causing the conflict.
At the same time, the Celestial Horde from Jupiter, as well as the Void Realm unified human mind entity that called itself true humanity, took the opportunity to attack Terra itself. Behind the war, as the death toll rose sharply, the restless dead within the Void Realm underworld also launched the Wall-Breaking Operation. Vast numbers of dangerous spirits broke free of the underworld's restraints and roamed between the Void Realm and the material world.
Not long afterward, the free organization known as the Gloomvale Army, acting in the name of the Gloomvale Knight, also began assassinating leaders from multiple factions. The Gloomvale Army possessed formidable technological capabilities. The new Aether Armor they developed wielded unimaginable power, and even possessed Nether Ruin Furnaces capable of breaking through the barrier between the material world and the Void Realm, granting them almost perpetual combat endurance.
Riding Nether Ruin Armaments, the Gloomvale Army launched surprise assaults on the Central Nexuses of major powers. Leikal Hadden, the fiftieth Federation