Eidolon (Final Fantasy XIII)

Eidolons are the summons in Final Fantasy XIII, a spirit belonging to only a single l'Cie whom they reflect in some matter. 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 SP (Summon 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, and the power of their finishing move increases as the player summons them more often in battle. Eidolons also have a connection with the Paradigm Shift roles their summoner can use when they join the party. 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
Snow's Eidolon, the Shiva Sisters, can become a motorcycle. Their concept is Rapid Blaster.

Gestalt moves:
 * Wheelie
 * Spinfreeze
 * Icicle Drift
 * Ice Ramp
 * Diamond Dust

Odin
Lightning's Eidolon, Odin, can become a horse. His concept is Multi-Attacker.

Gestalt moves:
 * Stormblade
 * Lightning Strike
 * Razor Gale
 * Thunderfall
 * Zantetsuken

Brynhildr
Sazh's Eidolon, Brynhildr, can become a sports car with side mounted machine guns. Her concept is Gadget Master.

Gestalt moves:
 * Chopper Spin
 * Caltrop Bomb
 * Centrifugal Sweep
 * Spark Shower
 * Múspell Flame

Bahamut
Fang's Eidolon, Bahamut, can become a flying dragon. His concept is Aerial Raver.

Gestalt moves:
 * Hunting Dive
 * Aerial Loop
 * Obliterating Breath
 * Pulsar Burst
 * Megaflare

Alexander
Hope's Eidolon, Alexander, can become an immobile fortress hugging one edge of the battlefield. His concept is Tactical Commander.

Gestalt moves:
 * Purification
 * Earthquake
 * Brutal Sanction
 * Retributive Blast
 * Divine Judgment

Hecatoncheir
Vanille's Eidolon, Hecatoncheir, can become a quadrupedal mech with four machine gun turrets. His concept is Shooting Blaster.

Gestalt moves:
 * Chain Cannons
 * Missile Tetred
 * Piercing Ray
 * Force Blasters
 * Gaian Salvo

Other Eidolons

 * Ifrit
 * Carbuncle
 * Siren
 * Ragnarok
 * Ramuh
 * Valefor

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.