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Prologue

Kaleidoscope: [kuh-lahy-duh-skohp]

-noun

1.) An optical instrument in which bits of glass, held loosely at the end of a rotating tube, are shown in continually changing symmetrical forms by reflection in two or more mirrors set at angles to each other.

2.) A continually changing pattern of shapes and colors.

3.) A continually shifting pattern, scene, or the like.

4.) The Second True Magic, the Operation of Parallel Worlds.

Consider every choice you have ever made in your life. Every decision you have ever made, a parallel analogue of you has made the opposite of it. Not all choices only have two options, however, and every single one of those options has been, is being, or will be explored by 'you' in a parallel world.

Before you get any particular feelings of empowerment, however, consider that the exact same situation is occurring with each and every one of the 6.8 billion plus humans on this planet and the untold numbers of non-human inhabitants of this world, both sentient and non-sentient.

But the planet Earth is not special in this regard. The observable width of the universe is 93 billion light years, or 8.79829142x10^26th power meters. But that is not the actual measure, only what can be observed/estimated at this time. In this unfathomable measure, untold trillions of galaxies, stars and solar systems, and planets exist, many of which have their own inhabitants, sentient and non-sentient, and their decisions likewise spawn parallel existences.

Then consider the realities where life never evolved on these planets; where random cosmic chance lead to the salvation or destruction of others. One could harness the power of every supercomputer on the planet, and task them with the single operation of calculating the exact number of alternate realities spawned in this manner, and they would never finish.

There is no way to know the exact number of realities or dimensions bound within the multi-verse, but one man, one being, is the only one who can be said to have travelled to and experienced more of these realities than any other.

Kischur Zelretch Schweinorg, the Wizard Marshall, Zelretch of the Gemstone, Dead Apostle Ancestor.

It is unknown just how old Zelretch is, or even where he originates from, only that he is the sole user of the Second Magic, "Kaleidoscope," the Operation of Parallel Worlds. It is unknown just what the full extent of the Second Magic is, but Zelretch used it to defeat Brunestud of the Crimson Moon, King of the Vampires several centuries ago, an event during which Zelretch gained immortality as he was unwillingly converted into one of the 27 Dead Apostle Ancestors.

The aspect of the Second Magic that we are most concerned with here, however, is its ability to create Multi-Dimensional Refraction Phenomena, or the ability to create openings into these parallel realities and interact with the 'Other Side.'

It is a common theory that Zelretch is responsible for most, if not all, of the crossover events that occur between realities. There is justification for this belief…for while Zelretch is first-and-foremost an observer of events, he does see fit to interfere in matters with his own hands from time to time. In fact, this theory is true, to a startlingly-terrifying degree.

Zelretch is an immortal being, 'Beyond the ken of mortal man,' to wax poetic. However, he first existed as a mortal human, and human minds are not suited for the rigors of eternity. Thus, in an effort to stave-off madness and boredom, Zelretch will find a new cluster of realities to observe. First, he will choose a reality and designate it as the 'Prime' reality. Then, Zelretch observes the spin-offs of that reality. Finally, Zelretch will interfere with one or more of these realities, in order to observe the ensuing chaos.

At the current moment, Zelretch is observing one particular set of realities, bound together by common natural laws, and has seen fit to introduce a new player into the events occurring there now. His choice is a relatively unknown individual, whom nevertheless has had a major impact in several realities, for good or for ill.

His choice, is Emiya Shirou.