Quantum Time-Lock

Quantum Time-Locks (霊子記録固定帯) are an existence implicated in the culling of parallel worlds. In Thaumaturgical Society, they are also referred to as Human Order Foundations (人理定礎).

Overview
Building off Human Order (人理) -- also known as the Common Sense of Man (人間の常識) -- the principle that attempts to make humanity last as long and vibrantly as possible, Quantum Time Locks are a set of fixed outcomes that are placed into history. Although the number of parallel worlds is infinite due to the unlimited number of choices that humans make, the amount of energy that our dimension has that would be used to sustain these parallel worlds is finite. In order to resolve this paradox, "locks" are created at certain points in time to create a standardized history among parallel worlds where the growth potential of humanity is maximized. Parallel worlds that do not lead to this standardized history have their energies cut and are destroyed. Only humans of the particular time period can affect how history will be a shaped when a Quantum Time Lock is placed; past or future interventions are powerless.

In the case that someone time travels to the past, although minor events can be changed, the outcome of history that is locked into place through Quantum Time Locks cannot. Although normally impossible, in the case that a Quantum Time Lock is forcibly destroyed and the course of human history is somehow altered, all history past the collapsed Quantum Time Lock is destroyed.

Fate/Prototype: Fragments of Blue and Silver
In the case that Manaka Sajyou succeeds in fulfilling Saber's wish of an eternal Britain, the Human Order Foundation collapses and the modern world is destroyed.

Fate/Grand Order
Solomon destroys the Human Order Foundation through his Singularities in the beginning of the story.