Having conquered the British Lostbelt and NFF HQ, Chaldea detects a massive Singularity with an immeasurable Humanity Foundation Value. It is a world split into three realms—each with its own king—where Servants are ceaselessly summoned to battle each other. Chaldea's Master is overwhelmed by the unthinkable sight of armies of Servants clashing ceaselessly. As if to make things worse, an unseen hand slowly but surely reaches out for Master. "Who could have done this, and why? Most importantly, how did they summon so many Servants?" This is not a typical mission into a Singularity. Who could this Master be? Some mysteries may be better left unsolved...