Heian-Kyou (Fate/Grand Order) Wiki

Naraka Mandala, Heian-kyou

The members of Chaldea return from their brutal struggle in the Fifth Lostbelt. As they prepare to begin their mission in the next Lostbelt, they detect a new Singularity, which is marked as a sign of Humanity's collapse. Until now, it had been believed that no such signs could be seen upon the bleached earth, where human history has come to an end.
It is in the Heian period in Japan. The splendid capital Heian-kyou enjoys tremendous prosperity under the enduring rule of the Fujiwara clan.
But after Rayshifting to what should be a time of plenty, Chaldea instead finds a world overrun by evil spirits and infested by horrid abominations. In this land, "Imperial Warriors" conduct a ritual modeled after a Holy Grail War.
Who are the Imperial Warriors, and what purpose does their ritual serve? In this mysterious, millennium-old city, Chaldea's Master faces the machinations of the Beautiful Carnivore.

A singularity that formed on the bleached earth in Fate/Grand Order, created and maintained by Ashiya Douman where he attempts to transition it into its own Lostbelt. It's set in Japan in A.D. 1008 and takes place following the events of Olympus. Released on the Japanese server December 4, 2020 and on the NA server on November 21, 2022.