Hecatoncheir (summon)

Hecatoncheir (ヘカトンケイル Hekatonkeiru) is Oerba Dia Vanille's Eidolon in Final Fantasy XIII. It is an Earth-elemental creature with multiple arms.

During its Gestalt Mode it transforms into a war machine with gun turrets that Vanille rides. The summon's gameplay concept is Shooting Blaster, and it's Gestalt Mode attacks are ranged and place a strong emphasis on the positions of the enemies in the battle. Its super move is Gaian Salvo.

Vanille and Fang will first face him as a boss, as a test to prove Vanille's strength to him.

Story
Fang becomes suspicious and decides to confront Vanille about their past. In order to get the truth out of her, she decides to lie and says that she finally remembers the events surrounding their previous Focus. She reveals that she was the one who became Ragnarok and scarred Cocoon many centuries ago. Although Vanille knows this is the truth, she frantically tries to deny it. As if to reprimand her for lying, Hecatonchier is summoned and confronts the duo. Fang interprets this as a sign of the truth, and Vanille finally admits what she suspected - Fang was indeed the one who transformed into Ragnarok in the War of Transgression. Vanille breaks down in tears, saying that she didn't want Fang to bear the terrible guilt of the beast's bloody rampage, though Fang forgives her.

Trivia

 * Despite the similarities, Hecatoncheir's Gestalt Mode is not inspired by the Magitek Armor from Final Fantasy VI, but ended up looking like it. Also, Vanille's pose on top of Hecatoncheir's Gestalt resembles Rikku and her Machina Maw dressphere.
 * In Final Fantasy III, Hecatoncheir is a boss in The Cave Of Shadows.