Fifth Ark The Fifth Ark is a decrepit building the party crashes into after escaping the " Palamecia " in " Final Fantasy XIII " . Fifth Ark originates from Gran Pulse whose fal ' Cie constructed numerous Arks that now lie hidden around the world . Their original purpose is shrouded in mystery , but it is known Arks were used to train l ' Cie to become strong enough to fulfill their Focus . The area contains tunnels with remnants of trains like present - day subways , and modern - day skyscrapers similar to those in the Yaschas Massif . The Fifth Ark is an unrevisitable location that comprises the tenth chapter of the game . Datalog . " This Gran Pulse structure lies deep below the capital city of Eden , its existence unknown to the members of the Sanctum . " " According to legend , Arks are Gran Pulse armories that hold living weapons in stasis , in preparation for war with outside forces . These facilities also supposedly serve the function of awakening a l ' Cie ' s latent powers . " " Why this ' Fifth Ark ' is on Cocoon , and whether there are other Arks hidden elsewhere , is uncertain . " Story . After the party escapes the " Palamecia " they are flown into a building below Eden that houses the Fifth Ark , a facility created by the Pulse fal ' Cie . The party wonders if they should complete their Focus to destroy Cocoon , or carry out Serah ' s wish to save it . According to Fang and Vanille , a Pulsian legend tells the Arks are facilities the fal ' Cie created to build weapons of war . Many had tried to search for the Arks but were unsuccessful . The Arks were used as training grounds to make l ' Cie stronger . The l ' Cie encounter Cid Raines and discover he is a Sanctum l ' Cie . Branded by the fal ' Cie Barthandelus , Raines ' s Focus is to aid the party destroy Cocoon under the fal ' Cie ' s guidance . Raines tells the l ' Cie the fal ' Cie wish to annihilate Cocoon so that " The Maker " would return to the world and make it anew . The fal ' Cie , unable to carry out this goal themselves , turn humans into l ' Cie while tending to the Cocoon populace preparing them to be sacrificed . Cid attacks the l ' Cie to foil the fal ' Cie ' s plan by killing the l ' Cie before they can destroy Cocoon . Cid is defeated and turns to crystal despite having opposed his Focus . Inspired by this , Snow decides he should defy his Focus like Cid did and try to save Cocoon like Serah had asked , even if it means he may turn into a Cie ' th . Voicing his views , everyone sides with him apart from Fang who does not want to see them turn into Cie ' th . She turns her weapon on the party , but unwittingly summons her Eidolon Bahamut . Lightning and Vanille help her defeat the beast . Fang speculates the Eidolons appear whenever a l ' Cie begins to waver on their path towards completing their Focus , forcing the l ' Cie to choose life or death . Fang yields to the others ' wishes when defeating Bahamut reveals a new path to the lowest level , where they discover an airship and a portal to Gran Pulse . Realizing it is their only way out they fly the ship through the portal and into the skies above Gran Pulse . The airship is destroyed by the local wildlife , sending the team flying out with Fang saving everyone by summoning Bahamut whom they ride down to the world below . Later , during the l ' Cie ' s assault on Eden , Pulsian Dreadnoughts and many species of Pulsian wildlife ( including Behemoths , Adamantoises and Amphisbaenas ) invade the area via transgates , due to ( what is speculated as ) the fal ' Cie activating the Fifth Ark below Eden . These are presumably killed during the battle and Vanille and Fang ' s transformation into Ragnarok . Enemies . In addition to the monsters listed below , two Phosphoric Ooze can merge into one Alchemic Ooze , an Imp can summon an Ahriman and a Berserker can forge a Centaurion Blade . None of these enemies award additional CP . Musical themes . " Will to Fight " is the background theme of the Fifth Ark . Etymology . The Ark is fifth of its kind , there being rumored to be thirteen in total .