Assassin (Fate/Zero)

"We are all acting as one Servant, and each individual is only a shadow of the whole."

- Multiple Assassins, Fate/Zero

Assassin is a villain from Fate/Zero who is the Servant of Kirei Kotomine during the fourth Holy Grail War. His unique trait is his capability of manifesting as multiple entities at once. They all act as bodyguards for both Kirei and Tokiomi Tohsaka.

Appearance
The multiple personalities of Assassin are able to vary widely in age, gender, build, and dress style, but in general, their hair appears purple, and their skin and clothing are nearly black. They all wear the standard skull mask associated with the known Hassan of other Grail Wars. Much like True Assassin, the female Assassin doesn't actually have a face underneath her mask even though she was given a design in Fate/Zero material.

Personality
Each of the Assassins has their own personality, and their experiences are not shared between them. The female Assassin is shown to be the main one to interact with Kirei. The Einzbern Consolation Room introduces the first Assassin to be killed by Gilgamesh as Zayd. Zayd has a polite tone of speech and a habit of pushing his mask up repeatedly when he speaks. He is very passionate and emotional, and gets upset that his only role was simply to die. He is eventually convinced to have more pride in his role, and vows to become Zayd, the King of Assassins, before dying in despair and seeing the others being slaughtered by Rider.