Great Twilight

The Great Twilight (イナル黄昏) is the phenomenon that occurred after the slaying of the Nameless One, causing the curse of Erebonia to cover the entire continent of Zemuria, amplifying and manifesting negative emotions.

The plan is succeeded by Operation Jormungand.

Preparation
First known preparations for the Great Twilight date back to approximately S.400, after Emperor Hector Reise Arnor I recaptured Heimdallr from Dark Dragon Zoro-Agruga. Before Black Alberich, leader of the Gnomes, cut ties with Roselia and the Hexen Clan, he shared a prediction about the end of the world with her and the then-Crown Prince.

Black Alberich stole the knowledge of the alchemists from Crossbell and handed them to the mages of Erebonia to stimulate the development of Magic Knights. He also collected data from weapons he has donated to jaeger corps, planned the Thirteen Factories for Ouroboros, gathered the best students of C. Epstein and gained control of Reinford Group.

It is unknown how much progress was made during this time period, and the plan in its current form is known to have been conceived around S.1186, when Giliath Osborne began working with Black Alberich. To secure the resources necessary to carry out the plan, Black Alberich as Franz Lughman married Irina Reinford and fathered Alisa Reinford. After his use for the Reinfords was fulfilled, he faked his own death at the hands of Sharon Kreuger. For the next twenty years, Black Alberich would provide Osborne with tools necessary to further the plan, including the homunculi Millium Orion and Altina Orion.

Observations by the Church
The Septian Church noticed small-scale, hardly noticeable disturbances in the septium veins coming from Erebonia. The Church decided to dispatch Thomas Lysander and Barkhorn to investigate the matter. After the Orbal Shutdown Phenomenon in Liberl, Azure-Zero Project in Crossbell, and the October Campaign in Erebonia, the disturbances grew worse with each event.

When Erebonia annexed Crossbell and North Ambria, the disturbances reached a point where it would spawn Magic Knights and Cryptids heralding from Erebonia in Crossbell, and where Pleroma Grass native to Crossbell started to grow in Erebonia.

Ouroboros' support
Following Osborne's "takeover" of the Phantasmal Blaze Plan in S.1204, the seven Anguis of Ouroboros voted on whether to continue with the plan as is, or to instead focus on completing the Great Twilight with Osborne and the Gnomes. The vote was 6-1, with only the Second Anguis, Vita Clotilde, choosing to decline. As a result, despite being the leader of the Phantasmal Blaze Plan, Clotilde did not participate in the Great Twilight.

F. Novartis, the Sixth Anguis, provided the participating members of Ouroboros with three Gordias-class archaisms. These three were the Aion Type-α II, Aion Type-β II, and Aion Type-γ II.

Beginning of the Twilight
Following the revival of Zoro-Agruga, and the hyper-stimulation of the septium veins, Black Alberich and Osborne, along with Ouroboros, were able to rouse the Nameless One from its slumber deep underneath Karel Imperial Villa. This resulted in the manifestation of the Gral of Erebos, which blanketed the entirety of the Heimdallr area in darkness, and caused multiple cryptids to spawn in the streets. At the bottom layer of the Gral, Millium Orion suffered fatal damage at the hands of the Nameless One, causing her soul to sublimate into the Sword of the End. Using this sword, Valimar slew the Nameless One, unleashing the curse upon the land, starting the Great Twilight.