The Holy Grail, an omnipotent wish granting device, has appeared. It has chosen seven Masters. The Masters will summon seven Servants to engage in mortal combat. The surviving Master and Servant will earn the right to have their wish granted by the Grail. The methodology the Grail uses to choose the Masters are unknown. Some Masters are Magus with knowledge of The Holy Grail War, while others are completely ignorant of the Grail and magic.
Masters! The Holy Grail has appeared. It has chosen the Masters, even if they do not know it yet. The Holy Grail War will be starting, but the first shots have yet to be fired. Let The Holy Grail War begin!