The Holy Grail is the ultimate goal of the Holy Grail Wars held in Fuyuki City. It appears at the end of the war to grant the final Master and Servant pair a wish on the Great Grail, the true device that has the power to grant wishes. Because it is only a vessel to summon the Great Grail, it is known as the Lesser Grail.
What is handed down in the city of Fuyuki isn’t the one that received the blood of Christ, but the prototype of an even more ancient “omnipotent container”; this container is the 726th Grail that sticks to the legend of the name. It is a gate that leads to the Root, Akasha; a hole connected to the nuclear core, the Great Grail, a wish machine. It is not an omnipotent container, but a replica created to work like a “wish machine” that can bring forth one’s own will.
Up until the third Grail War, the vessel for the Grail, also called the Lesser Grail, was a literal “cup”. However, during the events of the third War, it was damaged in battle and the ceremony was interrupted; for that reason, it had to be made as something that could manage itself and take care of itself.