>>98932968the world/universe in Fate is just the manifestation of the Root, an endless swirl of information that records all events past/present/future
the timelines are nonlinear, they can split, cross and parallel each other and due to interaction of various greater forces in the universe (like Gaia, Alaya etc.), only some of them are physically actualized
Alaya is the collective conscious/unconscious will of humanity to exists and that provides it both contact with humanity and access to its records, and based on these records it can either physically or spiritually actualize forces in places and times on Earth where humanity's total extinction is a risk (the so called Counter Force) and Emiya just became contracted to it so his record can be reused by it in places where using proper heroes would be too great of a bend in reality (because none of the forces involved are omnipotent aside from Root and they tend to try and remove their more overt influences, which can be prevented only by expending magic power)
