Theoretical fan-designed [[dark persona]] version of a character who has been (theoretically) corrupted by the mud of the Fuyuki Holy Grail from [[Fate/Stay Night]], similar to canon examples like [[Dark Sakura]] or [[Saber Alter]]. Fan examples of "alters" include [[Archer Alter (fate)|]], [[Lancer Alter]] (later made [[cu_chulainn_alter_(fate)|canon]] in [[Fate/Grand Order]]), or the "Sabatsugu" version of [[Emiya Kiritsugu]] (not to be confused with [[Emiya Kiritsugu (Assassin)]]).

Common traits of an Alter version of a character include [[white hair]], [[red eyes]] or [[yellow eyes]], [[pale skin]], and visible red veins of [[corruption]]. Alter characters will also typically be dressed in an [[alternate costume]] with darker colors or stripes of black and red.

In the later installments, the concept of Alter Servant is expanded to include any servant that were corrupted or have their saint graph altered to some degree without the Holy Grail involved. Notable examples include [[Atalanta Alter (fate)|]] who is essentially an alternate noble phantasm form of [[Atalanta (fate)|]] and retains the same personality.

The opposite of this is [[Lily Servant]].

Not to be used for official Alters, which include:

* [[Archer Alter (fate)|]]
* [[Arjuna Alter (fate)|]]
* [[arthur pendragon alter (fate)|Arthur Pendragon Alter]]
* [[artoria pendragon (lancer alter) (fate)|Artoria Pendragon Lancer Alter]]
* [[atalanta alter (fate)|Atalanta Alter]]
* [[Cu chulainn alter (fate)|Cu Chulainn Alter]]
* [[Dark Sakura]]
* [[Emiya Alter]]
* [[Galahad Alter]]
* [[Jeanne D'Arc Alter (fate)|]]
** [[jeanne d'arc alter (avenger) (fate)|Jeanne D’Arc Alter (avenger)]]
** [[jeanne d'arc alter (swimsuit berserker) (fate)|Jeanne D’Arc Alter Swimsuit Berserker]]
* [[jeanne d'arc alter santa lily (fate)|Jeanne D’Arc Alter Santa Lily]] (also counts as a Lily Servant)
* [[Marie Antoinette (Alter) (fate)|]]
* [[medusa (lancer alter) (fate)|Medusa Lancer Alter]]
* [[mysterious heroine x alter (fate)|Mysterious Heroine X Alter]]
* [[okita souji alter (fate)|Okita Souji Alter]]
* [[Saber Alter]]
** [[artoria pendragon (alter swimsuit rider) (fate)|Artoria Pendragon Swimsuit Rider Alter]]
** [[Santa Alter]]
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