Beast

Beast (ビースト) is a non-standard Servant class representing the evils of humanity. Rather than being Heroic Spirits that can be summoned by humans for use in Holy Grail Wars, they are the archetypes of the Heroic Spirit Summoning System - the personified self-destructiveness of mankind that act as the enemies of the Grand Servants. It is a cancer that grows with the advancement of civilization in order to rot it from the inside, and unlike the Avenger class that exists to eliminate humanity, it exists to be eliminated by humanity. There are seven Beasts in total.