|Character type:||Servant (Master: Manaka Sajyou)|
Beast's identity is the Beast of 666 (666の獣, ?) that was written of in the Book of Revelation from the Bible. It is said to be the beast who wears ten crowns symbolizing the sins and greed of humanity. The entire purpose of the Holy Grail War is to bring it into existence, planned by a heretic cardinal who stole an imitation Holy Grail from the Church. It is to be a new being of a higher level of existence incarnated through the Greater Grail, a cauldron to give shape to it due to the shape of the Grail originating from Christianity, by using the souls of seven Servants as an ignition charge.
Manaka manages to defeat all the other Servants in the First Holy Grail War and begins sacrificing various people to help manifest the Beast, somehow believing that Beast will help bring about Saber's wish. Saber kills her, but she later revives in a zombified state.
After the defeat of Sancraid Phahn and the battle between Saber and Archer, Manaka is shown to be actively incarnating Beast along with the Archer, Lancer, Rider, Caster, Berserker, and Assassin class Servants from the previous war. Manaka still seeks to use Beast to fulfill Saber's wish.