Hidden behind the thin veil of the modern world, supernatural beasts roam the world and men wield the powers of small miracles. Churches hide organizations of heretic and witch hunters wielding holy weapons, and hidden workshops conceal the life's work of modern day magicians.
Over the generations a great contest has been waged known as the Holy Grail War, in which magicians summoned the spirits of mighty heroes from ages past to do battle on their behalf. Their prize would be the Holy Grail, an object of infinite power that could grant any wish to the one who claimed it.
Many "bootleg" Grail Wars have been waged across the world, but the original Holy Grail was stolen in the 1930s with the assistance of German armed forces, who intended to use it to legitimize Germany's claim to the world. It disappeared in transit, stolen by the Yggdmillennia magus family.
The year is now 2004, and the Yggdmillennia family has declared a secession from the Mage's Association, the governing body of all magicians. To support their secession they've begun what is known as the Great Grail War. But things have not gone as planned, and few of their magicians have managed to lay claim to a servant. All around the world, magi are abruptly approached by great heroes of old calling them Master...
(Note!: This Fate theme treats the standard rules of the Nasuverse as guidelines at best, and should be considered wildly non-canon. It will probably break rules of the canon Nasuverse pretty regularly.)