Eidolon (Final Fantasy XIII)

Eidolons (召喚獣, shoukanju, lit. summon creatures) are the summons in Final Fantasy XIII, a spirit belonging to only a single l'Cie whom they reflect in some matter.

Datalog
''These mystical entities reveal themselves before only to a select few l'Cie. It is said that they are saviors, come to rescue hopeless l'Cie who find themselves bound to a Focus against their will. If this is true, they offer a brand of salvation few indeed would seek willingly: without exception, Eidolons attack the l'Cie whose presences they grace.''

''There have been no l’Cie in Cocoon for centuries, and as a result, no way of determining the truth behind tales of these beings. To the citizens of Cocoon, they remain the stuff of bedtime stories.''
 * &mdash; Datalog/History and Myth

Profile
Usually appearing when a l'Cie is in deep despair, an Eidolon appears to battle its l'Cie, immediately casting Doom on their respective summoner at the start, in order to give them second thoughts about wanting to die. After passing their test, the l'Cie can summon their Eidolons as allies soon after. They are summoned through TP (Technical Points) and fight alongside the summoning party member in battle while the other members temporarily leave. Additionally, one can activate Gestalt Mode (ドライビングモード Doraibingu Mōdo, lit. Driving Mode), a special ability that allows the Eidolons to change into a form the player can ride. When used by the player, it shifts the battle to a more action-oriented tone in which button inputs correspond to attacks.

The duration of the Gestalt Mode is determined by a gauge, and each attack subtracts a certain number of points from the gauge. It also allows access to the Eidolon's finisher, which immediately consumes all the points left in the gauge. Eidolons grow in strength as their summoner grows. Each Eidolon has a concept that defines their actions in battle.

When an Eidolon is dismissed in battle all party members regain maximum health and K.O. characters regain consciousness making them extremely useful as last resort.

Shiva
The Shiva sisters, Stiria and Nix, are Snow's Eidolons, obtained in Lake Bresha. They both have their own separate SP gauge and both will be dismissed if one of them falls to zero. In normal mode, Stiria focuses on a Medic and Ravager role, healing Snow and dealing ice-elemental damage on their enemies. Nix focuses on a Commando role, as her abilities are physical based, although she does have one spell at her disposal. While Stiria cannot be targeted by enemies, she can still be damaged by area-of-effect attacks.

In Gestalt mode, the Shiva sisters transform into a motorcycle. Their concept is Rapid Blaster.

Odin
Odin is Lightning's Eidolon, obtained in the Vile Peaks. Odin is lightning-elemental in nature and has many powerful and diverse physical and magic attacks. He also acts as a Sentinel, drawing all enemy attacks. As Odin has difficulty in driving up enemy chain gauges, it may be better to place Lightning in the role of Ravager to increase Odin's Gestalt gauge.

In Gestalt mode, Odin transforms into the horse Sleipnir, named after Odin's horse in Norse mythology. His concept is Multi-Attacker.

Brynhildr
Brynhildr is Sazh's Eidolon, obtained in Nautilus. By default, Brynhildr is Fire-elemental, but Sazh can bestow En– spells on Brynhildr allowing her to change her elemental characteristics. However one of Brynhildr's drawbacks is that all her abilities are physical based.

In Gestalt mode, Brynhildr transforms into a sports car with side mounted machine guns. Her concept is Gadget Master.

Bahamut
Bahamut is Fang's Eidolon, obtained in the Fifth Ark. Bahamut utilises powerful non-elemental attacks, making him the Eidolon with the highest damage-dealing potential. However as Bahamut's SP is rather low compared to other Eidolons, it may be a good idea for Fang to assume the role of Sentinel to increase the summoning time as well as boost Bahamut's Gestalt gauge whenever Fang is attacked while blocking.

In Gestalt mode, Bahamut allows Fang to ride him. His concept is Aerial Raver.

Alexander
Alexander is Hope's Eidolon, obtained in Vallis Media. Like Bahamut, Alexander also utilises strong non-elemental attacks, however they are all physical based. Alexander draws in all enemy attacks and has the highest starting SP of all Eidolons. Another drawback to Alexander is that he is very slow moving around the battlefield.

In Gestalt mode, Alexander transforms into an immobile fortress hugging one edge of the battlefield. His concept is Tactical Commander.

Hecatoncheir
Hecatoncheir is Vanille's Eidolon, obtained in Mah'habara Subterra. Hecatoncheir is Earth-elemental and is the only Eidolon that possesses the Quake ability. However he is also the only Eidolon that doesn't have Curaga, meaning Vanille must heal for herself.

In Gestalt Mode, Hecatoncheir transforms into a bipedal mech with four machine gun turrets. His concept is Shooting Blaster.

Music
When fighting Eidolons, there are two possible battle themes that will accompany the fight. "召喚獣" (named in the English tracklist as Eidolons) plays during Snow's battle with the Shiva Sisters, Fang's battle with Bahamut, and Vanille's battle with Hecatoncheir. "世界の敵" (named in the English tracklist as Test of the L'Cie) plays during Sazh's battle with Brynhildr and Hope's battle with Alexander. Lightning's battle with Odin is the only one in which neither theme is featured, instead being accompanied by "死闘" (named in the English tracklist as Desperate Struggle).

Etymology
"Die Gestalt" is a German word for "form" or "shape". It is used in English to refer to a concept of "wholeness" in which the whole is greater than the sum of its parts.

Eidolon (Final Fantasy XIII)