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. Starting off uncontrollable, an Eidolon must be tamed in a battle by its l'Cie before becoming an ally to him or her. However, the battle will be not an easy one. The Eidolons will immediately cast Doom on their respective summoner at the start of the battle, so they must defeat them before the spell counter reaches 0, or they will lose the battle automatically. 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 rideable form. 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.

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

Gestalt moves:
 * Thunderblade
 * Shockblade
 * Razor Gale
 * Thunderfall
 * Zantetsuken

Shiva
Snow's Eidolon, the Shiva sisters, can become a motorcycle. Their concept is Rapid Blaster.

Gestalt moves:
 * Wheelie Flash
 * Splash
 * Icicle Turn
 * Air Edge
 * Diamond Dust

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

Gestalt moves:
 * Gatling Cannon
 * Tetra Missile
 * Penetrate Ray
 * Buster Force
 * Gaia Salvo

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

Gestalt moves:
 * Rotor Spin
 * Caltrop Bomb
 * Sweeping Turn
 * Hot Rod
 * Múspell Flame

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

Gestalt moves:
 * Earthquake
 * Holy Judgment

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

Gestalt moves:
 * Hunter's Dive
 * Aerial Loop
 * Baneful Breath
 * Pulsar Burst
 * Megaflare

Other Eidolons

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

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.