|Voice actor:||Mamoru Miyano|
|Character type:||Servant (Master: N/A)|
|Hair color:||Dark Red|
|Eye color:||Yellow Green|
"For him, who wished for the happiness of everyone... ---- For his sake, I will kill you all."
Rider has short wavy dark red hair and wears a gray mask with black markings to conceal his face and his identity, along with a black cloak.
At school he has stylish hair and yellow green eyes, and wears the navy school uniform with a white shirt, orange tie, and gray pants.
While he is the only one of the seven summoned Servants to not have had a tragic ending in life, he now welcomes gory deaths after the form of the boy, who wished only peace for everyone, has buried itself in his heart and drives him on his insane killing sprees. He never wipes away his smile when showing his true face, but he knows his actions are the opposite of what his Master wished. Even still, he has decided that he will kill again and again for the sake of his Master's happiness, all while showing a face streaked with bloody tears that will not stop.
He attends Ayaka Sajyou's school and disguises himself as a normal high-school boy, showing his two-faced nature. He is the popular boy of his class due to having a modern sort of beauty, getting along well with others, and being gentle. He portrays himself as an overall good youth who is polite, emotional, and easily gets teary-eyed. His fault can be said to be that he tends to overindulge in the things that he likes to the point that he consumes them all at once.
Rider is a Servant that was to be used in the original Fate/stay night novel that was penned and left uncompleted. He was only briefly mentioned in notes detailing the plot of the novel, and received an expanded role in Fate/Prototype. He was later redesigned and briefly shown in Fate/hollow ataraxia.
His Master is a 10-year-old boy, a victim of a "chimerization" experiment by the unknown antagonist of the last War. At the beginning of this War, he is entirely sustained by medical machinery. Rider hated the magus for being weak, but sympathized with his plight, and later became good friends with him. On the 7th day (the day the youth's life burned out), his Master used all his Command Spells, and made Rider fully incarnate, feeling that as Rider was someone who found happiness in life, his wish, the wish of a content man, will be a happy prayer to warm the heart of many. Moved, Rider fought alone for the one wish to resurrect his Master and grant him the happiness that a man should experience. His Master was the Third Master of the Holy Grail War and his Command Seal was located on the palm of his left hand, taking the form of a five-winged symbol.
With this, Rider dons a mask and disguises as a Master, joining the carnage that is the Holy Grail War.
Later, Caster sieges the school by throwing it into an alien realm. Both Rider and Ayaka are under assault, but because Rider is somehow connected to Caster he is able to save both of them by covertly dismantling Caster's alien realm.
Rider later faces off with Saber, after the priest informs Saber and Ayaka that there are some disturbances in the industrial area.
Rider owns a wide selection of Noble Phantasms of varying ranks, but he has a limit that allows him to use only one at a time. They include Sandals that fly through the air, the Mantle, a helmet in the myth, that changes and obscures the appearance of the wearer, the bronze mirror-shield given to him by Athena that allows for radar and sonar detection, the snake hunting sickle, Harpe, Kibisis, the sack that stores the head of monsters and a mirror world-type Bounded Field, and the Pegasus-handling bridle, Bellerophon.
He most often uses the mantle and a mask to hide his true form when acting as a Servant. The mask acts as a fake Master that supplies him Prana. In order to obtain the prana, he has to kill over and over in order to eat the souls of people. He is given a physical form by his Master while on the verge of death in order to challenge Saber.