When Illya tries to stop the ritual to activate the Holy Grail, a young boy brimming with confidence appears before her, acting like he sees through everything. He calls Miyu "Miss Princess From A Parallel World"! Who is the eight Class Card?! Where did Miyu even come from?! With the appearance of this young boy, the viel covering the truth is torn off.
It's most likely the same thing that was 
producing infinite Noble Phantasms.
Ich glaube, daher kam das Noble Phantasm.
Debe ser lo mismo que producían 
esos Fantasmas Nobles infinitos.
Debe ser lo mismo que producían 
esos Fantasmas Nobles infinitos.
À tous les coups,
Penso sia la stessa cosa con cui materializzava 
quell'infinità di Strumenti Preziosi.
Provavelmente a mesma coisa que estava
 criando todos aqueles Fantasmas Nobres.