True Assassin (Fate/stay night)

The True Assassin is a villain from Fate/stay night. He is an exceptionally dangerous Servant with a limited appearance in both said title and Fate/hollow ataraxia but has an expanded role in Fate/Zero. The designation of "True" is meant to distinguish this Assassin from the one that Caster summoned which not only broke the rules of the fifth Holy Grail War but also saw to it that said Assassin usurped this one's place in the war. All True Assassins share acollective identity and have appeared in every Holy Grail War throughout history. They are all infamous for wearing an ebony and tattered costume, as well as concealing their identity behind an ashen skull mask.

This Assassin, in particular, was summoned by Zouken Matou through the use of the corpse of Caster's Assassin-class servant as a catalyst in the Heaven's Feel route, which was True Assassin's only appearance. Zouken did so because he was disgusted by Rider losing to Saber and enraged at his grandson Shinji Matou's incompetence, so he decided to enter the Holy Grail War and summon True Assassin. True Assassin later attacks and devours Lancer to gain the ability to speak normally.

The Miracle Elite Storyline

Trouble in London

He was controlled by Shadow King as his class servant. Along side with Morpheus, Atman, The Groke, UBOA, and Moon.

Relationships

Android 21

True Assassin's one hit kill attack that involves using his cursed arm to create a fake heart. When he crushes the fake heart it's damage is reflected to fatally wound the enemy he fights against. He needs to be close to them to use this move. Anyone with magic resistance and have hearts with curses on them are resistant to this attack.

"True Assassin and Kishin Asura"

"Nagito Komaeda and True Assassin"

Zabaniya: Delusional Heartbeat

"Xenovia Quarta and True Assassin"