False Rider

Rider (ライダー) is the Rider-class Servant summoned by Kuruoka Tsubaki in the False Holy Grail War of Fate/strange fake.

Identity
Rider is the embodiment of Pestilence given form by the False Grail. Differing from those called Heroic Spirits, "he" is only one in name. Far from a "hero", "he" cannot even be called a Villainous Spirit or Demonic Spirit. Some regions have called "him" a "curse", and some religions have denoted "him" to be "divine punishment." "He" is Disease (病), that which has existed since time immemorial and that which will continue to exist far into the future. "He" has lived a shorter life than anyone, and yet has lived a longer life than anyone. Called a horseman who has brought calamity to all, "he" is that which "let loose" the Black Death that killed thirty million people and came "under the name" of Spanish Influenza that killed fifty million people. Given a physical presence despite not being a Heroic Spirit, "he" continues to exist in that moment to take the lives of those on the planet to provide "himself" nourishment for life to begin anew.

Role
Rider's master, Kuruoka Tsubaki, is the child of magi who are part of the US organization. In addition to studying the Grail War, they looked upon Zouken Matou's work on magical worms and attempted to improve upon it. They infected Tsubaki with a magic-based Bacteria as an experiment to better circulate magical power, and though it put her into a coma, it created an exceptionally powerful Master out of her. They only cared about their experiment and placed her into a hospital, while planning to use her as a puppet Master. They summoned the First Emperor of China as a Servant, though it was instantly devoured from the inside by Tsubaki's true Servant, Rider.

Abilities
Disease is something that rides on wind, waters, birds, and people, so it can be said that the Rider class is an appropriate designation. "He" is that which has "ridden" "his" way to dominance all over the world, and possibly most of all by being given an alias by the populace to reflect "his" nature as the embodiment of calamity, "he" has been summoned as such. "His" very nature is a foreign abnormality that proves the False Grail is the least worthy object for the title of "Holy Grail." It is unknown if anyone can even recognize "his" alias or even the fact that he has been summoned as a Servant in the first place.