Within the Fuyuki Holy Grail War system, it is said only the Hassan-i-Sabbah, summoned with the word "Assassin" as the catalyst, are applicable to be summoned due to them being the only true assassins to actually be recognized as Heroic Spirits. The Assassin in Fate/stay night, summoned by Caster, is an exception. He is an aberration in the system as another Servant summoned him. While he has Presence Concealment, it is his own ability rather than a Class Skill, and he appears listed as "Assassin?" in the Fate/complete material III Servant section. Heracles, even within the Fuyuki system, has qualifications for all classes besides Caster, so it is unknown how he would fit into the role of Assassin. The rule originally remained in the Great Holy Grail War system, but Masters eventually managed to bypass it after the abilities of all nineteen Hassans became known. The Moon Cell Holy Grail War of Fate/Extra does not mention any such rule ever having been in place.
Servants possessing the Class of Assassin for special reasons unrelated to a proper summoning.
|Arjuna (Fake)||Grand Order||Joan of Arc (Alter)|
|Nitocris (Swimsuit)||Grand Order||Protagonist|
|Scáthach (Swimsuit)||Grand Order||Protagonist|
Other qualifying heroesEdit
|True Name||Current Class||Notes|
|EMIYA||Archer||Fate/Ace Royal only|
|Hassan of the Quaking Pipe||N/A|
|Hassan of Shadow-Peeling||N/A|
|Medea||Caster||Fate/Ace Royal only|