After briefly explaining his idea, Gu Mo gave Ilya some time to think and turned his head to seriously examine the underground hollow in front of him.
As its name suggests, this place is called the "Dragon Cave"—
As the name implies, it's a cave where dragons dwell. This isn't entirely wrong; the term "dragon" doesn't necessarily refer to a specific creature but is an alternate name for a Spirit Vein, just as Spirit Veins and Earth Veins are also known as Dragon Veins.
This name already implies that this is indeed the nexus of magic power flowing through the land of Fuyuki, which is why the Great Holy Grail is set here. This massive magic circle is connected to Fuyuki's Earth Vein, drawing magic power from it to conduct the Holy Grail War, wielding the power to interact with the "Seat of Heroic Spirits" and summon Heroic Spirit Divine Spirits in the form of Servants.
It's truly the foundation of the Holy Grail War.
