Lostbelts

"The roots of Fantasy Trees will fall. The signal from heaven shall be cut off. The plane on Earth turns into solid ice. This planet has already left alone. This planet will turn into nothingness after they filtrating the alternate histories and starting an invasion. The rightful order has been lost. There's no Hero Spirit that guards humanity. The allies will fade and die. In this world, YOU are the real Evil of Humanity! However, on the point of survial, there's no superiority or inferiority between good and evil. If all of you don't ever give up, just act like before. Even if everything turned into nothingness, you'll still desire its survival! Fools, screech with all your might! Be remorseless over the faulty you accumulate. Be in debt for your responsility and eventually, fill your heart with hope. The battle for humanity is just begun."

- Goetia (under the persona of Solomon) to the protagonist, prophecizing the war in Lostbelts in the preview trailer of Cosmos in the Lostbelt

Lostbelts (異聞帯) are the main setting in Fate/Grand Order: Cosmos in the Lostbelt As opposed to the Greater History of Man, the history of 'winners' born from correct choices and proper prosperities leading to the "present", the history of 'losers' born from the wrong choices and mistaken prosperity is cut off. Considered "unnecessary" and cut off from becoming even parallel worlds, this history which has hit a dead end is known as a Lostbelt.

Overview
Following the attack on Chaldea in 2017, the freezing of the world and the declaration of rebellion against the Greater History of Man, with the threat of a regression into the Age of Gods and the recreation of the world, the survivors are forced to use an experimental method of navigating through imaginary number space, through the Lostbelts, in order to resolve the incident.

After all of the Lostbelts have been established, the Crypters seek to expand the "domain" of their own Lostbelts, which will eventually clash with the other Lostbelts. The one that is built by greater Human Foundation will end up overtaking the weaker one and use it as "nutrients". This process will allegedly continue, until only one Lostbelt is remaining.