Fate/strange Fake

The plot centers around a Grail War faultily copied from the Third Holy Grail War in Fuyuki. After the end of the third Grail War, an organization from the United States that has magi separate from the London-based Mage Association as members took data from Fuyuki's Grail War and planned their own ritual. After seventy years, they used the city Snowfield as the Sacred Land for their own Grail War. They were unable to successfully copy every aspect of the ritual, which lead to it acting only as an imitation that has lost the Saber class and allowed for the summoning of strange Servants due to the definition of a "hero" being blurred.

(Source: Type-Moon Wikia)

Originally conceived as an April Fools joke on Narita's homepage, the text, titled Fake/states night, was removed following April 1, 2008. It was later released in a revised novel format included with the second volume of TYPE-MOON Ace (2009). In 2015 it was officially published as a light novel by Kadokawa under Dengeki Bunko label.