A chronicle of the climax and aftermath of Fate/EXTRA, as used in Extella.
The Main Character, with the help of main Servant Nero and support Servant Tamamo no Mae, emerged victorious from the Holy Grail War, and advanced to the Moon Cell core.
However, Tamamo got separated on the path to the core due to certain obstacles, and only Nero and the Main Character arrived to face off against their final foe, Twice E. Pieceman.
After defeating Twice, the Main Character entered the Moon Cell core and interfaced with it.
By invoking the Holy Grail, the Moon Cell’s “wish-granting” power, they altered the state of the virtual world known as SE.RA.PH.
However, when the Main Character touched the core, the Moon Cell identified the Main Character’s data as a violation and began to delete it.
These are the events that unfold at the end of Extra.
…Or at least it should have been that way. But when the format of the Holy Grail War (which had deleted the defeated participants and obliterated Als without exception) was changed, the Moon Cell’s logic [decision] was changed as well.
The Main Character had wished to stop the vicious cycle wherein those who fulfilled their roles were removed and reformatted to serve in the next War.
Going forward, those who fulfilled their roles would seek new purpose. They would place equal importance on existing for their goals and finding a reason to live.
Thanks to this critical change, the Main Character was allowed to live as well.
According to the new settings, the Moon Cell began to weave together the individual sections of SE.RA.PH and created a new land. It was the inception of a world that would grow and thrive in virtual space alone. The Main Character was sent back to SE.RA.PH, and as the sole human in the new virtual world, found new expectations and responsibilities waiting…
With the old rules abolished, and constant collisions of regions coming together, the new SE.RA.PH was thrown into a state of constant confusion.
The Main Character continues on with Nero (and Tamamo no Mae), to explore the ever-expanding world of SE.RA.PH, while searching for a new goal and a place to call home.
Unbeknownst to the Main Character, the Moon Cell had long ago calculated that the great harvester, the Umbral Star, was once again approaching the Milky Way galaxy. It devised the Regalia system as a way to combat the Umbral Star, and summoned the Main Character to the core of the Moon Cell as both the sole human on SE.RA.PH and the representative of all life on Earth.
The Main Character learned of the Umbral Star from the Moon Cell, and agreed to protect SE.RA.PH.
After the Main Character gained authority over SE.RA.PH with the power of the Regalia, he or she planned to return to Nero straight away, but then the system administrator Archimedes made his appearance.
He hastily explained to the Main Character that they were in a state of emergency, and that a terrible threat was stirring in the Zero Dark, the scar that the Umbral Star left within the Moon Cell 14,000 years ago.
He suggested that they head there immediately, use the Regalia to reseal the Zero Dark, and return to Nero afterwards.
The Main Character joined Archimedes and headed to the oldest layer of SE.RA.PH.
What they witnessed there, in that limitless darkness…
…led to the beginning of Extella.