Great Disaster

The Great Disaster (大災) is one of the four major disasters, taking place in the Sacred Vollachia Empire approximately one year and five months after Natsuki Subaru was summoned to the world. Its prognosis is a driving force behind Arc 7 and it is a major event that takes place during Arc 8. Directly preceding the disaster was the Decisive Battle for the Imperial Capital, a battle for control over the Lupugana between the Imperial Army, the Pleiades Battalion, and the Rebel Army.

According to Ubilk, a Stargazer of the Empire, the Great Disaster could only commence after the death of Emperor “Vincent Vollachia”. In a confrontation between Vincent Abellux and Chisha Gold during the ongoing battle, the latter was killed by Balleroy Temeglyph, a dead man who had formerly been the Ninth among the Nine Divine Generals. Balleroy, along with all the deceased of Vollachia, were brought back as zombies by the bearer of the Great Disaster, Sphinx, a copy of Ryuzu Meyer who was created from the Witch of Greed’s failed immortality experiments and was a driving member of the Demi-Human Alliance during the Demi-Human War. With Chisha’s death, the Great Disaster commenced.

Background
More than 40 years before Subaru's arrival to the world, a member of Vollachia's Imperial Family named Stride Vollachia fell sick and spent three months on the border between life and death. After conquering his illness at the cost of his body beginning to resemble a living corpse's, Stride began to believe in entities known as the “Observers”. He wrote a journal containing contents about them and the signs of a future Great Disaster to come. Stride soon concealed the journal inside the Crystal Palace's library, and for undisclosed reasons, his name was erased from the records of the Imperial Family and the Vollachia Empire.

In the same era, the future bearer of the Great Disaster, Sphinx, was taking part in the Dragon Kingdom of Lugunica's Demi-Human War. She had once been used in a failed immortality experiment by Echidna, but after acquiring parts of the Witch of Greed's soul, she found her way into the world and happened upon Valga Cromwell nearly 350 years after her creation. She joined the Demi-Human Alliance at his beckon and gained infamy as the only “Witch” besides Satella whose name was engraved into the history of the Kingdom. However, during a battle for Lugunica Castle, Sphinx was forced to retreat and found herself taken captive by Leip Barielle, who she would be held prisoner by for over 40 years. Although she attempted to further her plans through two occasions while being trapped, these both failed. Consequentially, Sphinx settled on targeting Vollachia with the plan of destroying the Empire.

When he was a child, Vincent Abellux discovered the hidden journal of Stride Vollachia, which contained foreknowledge of the Great Disaster. He used it before and after becoming Emperor in an attempt to minimize the ruin it caused after ascertaining that it was inevitable. Many of the actions Vincent chosen, including his recruitment of Chisha Gold and Cecilus Segmunt, saving Prisca Benedict's life, his reforms to the Empire after becoming the Emperor, and the reestablishment of the Nine Divine Generals, were all for the purpose of minimizing the Great Disaster's ruin.

Trivia

 * The name “Great Disaster” is not exclusive to the modern incarnation of the disaster. Long ago, at an unknown time in the past, Lupugana's Magic Crystal Cannon once destroyed a large city, and according to legend, it was used in an incident also known as a Great Disaster.