gacha

fuyuki grail wars happened
or atleast the third war
So Requiem World is a World that takes place after the 3rd Fuyuki Grail War
Normal People got involved in this and Mosaic City were made as a response to this conflict as a safe place for refugees from the war
During this event more than 30 different Holy Grail Wars were happening simultaneously
If one person wins the war, they go to another area with the Grail to declare war and essentially became like freaking Tournament.
And as a result nearly no Sea Life Survived cause they were wiped out
And as the War got worse the World ,became all separated/divided
And the Mosaic Cities are essentially a Safe Space where a Barrier is protecting the Citizens and Refugee of the War
And outside of the Mosaic City is essentially a Hellscape
Where Wars are still happening.