|Appears in:||Fate/strange fake|
|Character type:||Servant (Master: Kuruoka Tsubaki)|
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.
Rider is not based on a hero, or even a human, so "he" lacks a persona and was only given knowledge by the system of the Holy Grail War. 'He" does not understand human emotion, and "he" only acts for Tsubaki and his own instincts. "He" is akin to a robot created without emotions or internal monologue, a mere formless mass of awareness and knowledge about the Holy Grail War. "He" speaks with a grating sound like the "scraping noise of swarms of insects battling one another" and his words are dread incarnate.
Rider is summoned by Kuruoka Tsubaki inadvertently after she gains Command Spells in the real world and invokes the summoning ritual in her dream world with her desperate pleas for her parents not to leave her alone. Despite "his" nature, she is not scared of "him" because she will no longer be alone. After she introduces herself, "he" takes her parents into the dream world, "dancing" together to forget her abuse and grant her desires. Though she smiles at "him" and thanks "him", "he" merely continues to exist without even giving a nod in reply. It is possible that the Player may be trapped within the dream world and attempt to escape.
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. "He" is noted to have great strength that makes his Master the dark horse of the war.
Rider appears within Kuruoka's dream world, letting loose a black fog over the streets. The contract is formed only within the dream, so none outside are aware of it. "He" is able to facilitate her unconscious dream magecraft by bringing people into the dream world by infecting them from outside, many black spots like bruises appearing of their bodies, and causing them to fall unconscious. While also absorbing their magical energy instinctively, "he" does not take directly from their life force, so their bodies are only disabled. They appear within the dream world with the same black spots covering them, and "he" manipulates them to remove their original personalities and instead become living dolls following Kuruoka's idea of how they should act.