Eidolons (幻獣, Genjū?, lit. Phantom Beast) are magical creatures called into battle by a Summoner. They were translated as "Summoned Monsters" in FFIV. Eidolons are the name of summons in several Final Fantasy games: all versions of Final Fantasy IV beginning with Nintendo DS, Final Fantasy IX, Final Fantasy XIII, and Final Fantasy Dimensions.
- Main article: Eidolon (Final Fantasy IV)
Originally they were known simply as "Summoned Monsters", with name change applied since the Nintendo DS version, Eidolons are a race of intelligent monsters that live in a separate world known as the Feymarch. Rydia is the only party member who can summon Eidolons.
- Main article: Eidolon (Final Fantasy IX)
Eidolons are massively powerful creatures in Final Fantasy IX, with enough power to destroy whole cities. For that reason, they are targeted by people greedy for power. The people of Madain Sari are the only ones who can summon Eidolons, unless their power is extracted into gemstones. Eidolons play major roles in the game's plot. Dagger and Eiko are the only party members who can call forth Eidolons.
- Main article: Eidolon (Final Fantasy XIII)
Eidolons in Final Fantasy XIII are magical beings that can be summoned by people made into l'Cie. Each Eidolon is unique to their summoner, because they reflect the summoner's personality. They have the power to transform into mechanical devices via a system called Gestalt Mode.
There are six playable Eidolons in the game, and several non-playable ones. It is said that Eidolons appear when a l'Cie's will to finish their Focus wavers, and the l'Cie must face their Eidolon in battle to gain their power.
- Main article: Eidolon (Type-0)
"Eidolon" is used as the official translation for the original term "War God" (軍神, Gunshin?) in Japanese. Eidolons are created by the Dominion of Rubrum as a part of their primary arsenal, and notably there are multiple variations of the same creature, who all belong to a certain Eidolon Class. Eidolons are normally summoned at the cost of the summoner's life, and only Special Eidolons can be summoned without endangering the summoner. The ability to summon these majestic creatures proved too much of a loss to its users. At one point, a summoner had to use the lives of an entire town to summon a Grand Eidolon, thus resulting in a tragic situation which forced the magic to become sealed.
- Main article: Eidolon (Dimensions)
Dissidia 012 uses the term "Eidolon" to refer to any summons from games that previously only referred to them as 'Summons'. Even Vaan refers to them as Eidolons when facing Yuna, despite Vaan knowing them as 'Espers' and Yuna as 'aeons'.
Eidolon is a Greek word for "unsubstantial image" or "phantom", additionally meaning "ideal", from which the Latin word Idolum comes. Idol is "a representation or symbol of an object of worship".