Soul (Fabula Nova Crystallis)

Souls are an integral part of the Fabula Nova Crystallis: Final Fantasy subseries, forming a core part of the motivations of the deities of the mythos, and often features predominantly in the games, linked to both the deities and the roles of humans, fal'Cie and l'Cie in their plans.

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The appearance of souls across the games in the Fabula Nova Crystallis series varies. In Final Fantasy XIII, the souls of humanity appear as glimmering crystals in the air in preparation for journeying through Etro's Gate. They also appear in this form in XIII-2, although they are not mentioned in much detail. In Lightning Returns, they appear as glowing lights similar to the pyreflies of Final Fantasy X, although they also appear in their crystalline form.

In Final Fantasy Type-0, souls appear to be synonymous with the substance known as Phantoma. It appears in various colors, but always as a smoke-like substance that flows out of enemies when they are killed. They can also be given willingly for some cause, as seen in the scene when the l'Cie Caetuna uses the willingly-surrendered Phantoma of hundreds of soldiers from Rubrum to summon the Grand Eidolon Alexander. In XV, soul appear to be similar in form to those in Final Fantasy XIII, although it is unknown whether they vary in appearance or not.

The souls of humanity were given to them by the Goddess Etro, primarily due to her sympathy with them because they were destined to follow her into the Unseen Realm. Because of this, they bear a strong link to the Unseen Realm, and those with the strongest connection can use magic without being made l'Cie. As stated in Lightning Returns: Final Fantasy XIII, the deity Bhunivelze, and likely his creations Pulse and Lindzei, are unable to see souls because of their strong links to chaos. Bhunivelze also despises this link, seeing it as a polluting force.

Mythology
The souls of humanity were given to them by Etro. Humans were originally soulless, created by Lindzei from the remains of Etro after the latter's suicide. After Etro was intrusted with keeping the balance between the Visible and Unseen Realm by the creator goddess Mwynn in her final moments, Etro, who felt an affinity with humanity as they were born from her blood and would follow her in death, gifted them with pieces of chaos. Because of this, humans became the key factor in sustaining the balance of the universe: their souls, made from chaos, pass into the Unseen Realm when the body dies, and are eventually returned in a new form, creating a constant cycle that kept the level of chaos constant.

Final Fantasy XIII
The key part of the Cocoon fal'Cie's plan to open the way to the Unseen Realm is to use Ragnarok, a monster born from a Pulse l'Cie. to destroy Cocoon's heart, the fal'Cie Orphan. This would send the planetoid crashing onto Gran Pulse, the plane below, causing cause the death of everyone on Cocoon and creating a flood of souls to force the door open. The first attempt, during the War of Transgression, is foiled by Etro when she sends the chosen l'Cie, Oerba Dia Vanille and Oerba Yun Fang into crystal stasis.

For the second attempt, the Pulse fal'Cie Anima ends up awakening Fang and Vanille, then branding Lightning, Snow Villiers, Serah Farron, Hope Estheim and Sazh Katzroy as l'Cie bearing the Focus to transform into Ragnarok. During the Siege of Eden, the souls of humans killed in the conflict gather around Orphan's Cradle in preparation for their journey through Etro's Gate. Eventually, after Orphan's destruction, Fang and Vanille accept their Focus to become Ragnarok, but use their energy to prevent Cocoon's fall and save both worlds, stalling the plans of the fal'Cie.

Final Fantasy XIII-2
The release of souls again form a crucial part of the game's plot. The overall plan of Caius Ballad is to force open Etro's Gate and unleash chaos into the mortal world. Although he ultimately succeeds by killing Etro by stabbing the Heart of Chaos, he also sets up a plan to topple both the old Cocoon and the new manmade Cocoon, triggering the flood of souls planned by the fal'Cie. When Serah and Noel arrive in New Bodhum in the year 700 AF, crystalline shards like those seen during the Siege of Eden float freely in the air. The soul of the seeress Paddra Nsu-Yeul also plays a crucial part: she was the first human created and was unable to fade into the sea of chaos like other souls. Etro, taking pity on her, put her in an endless cycle of reincarnation. However, this act meant that fragments of Yeul's soul and personality splintered off and created a source of chaos in the Visible Realm. This imbalance between the Realms causes the time distortions of XIII-2, and leads to the events of the entire game.

Lightning Returns: Final Fantasy XIII
In the aftermath of the merging of the Visible and Unseen Realm into Nova Chrysalia, Bhunivelze chooses Lightning as the savior. Her task was to rescue the souls of Nova Chrysalia in preparation for their life in a new world: in reality, Bhunivelze wishes to purge the rescued souls of their dark sides while destroying the souls of the dead, revealed to be able to return in new forms because of the memories held by the living. On Nova Chrysalia's final day, Lightning manages to disrupt the ritual meant to destroy the souls of the dead, and Vanille, who gains the power to hear them, frees them in preparation for their rebirth. This act prompts Bhunivelze to prepare to purge them himself, but Lightning's rebellion against him halts his plans. After they are freed from his control, the souls of humanity unite and deliver a final blow to Bhunivelze. All but one version of Yeul stay to maintain the balance between worlds in Etro's stead and the souls of humanity, along with Lightning and her friends, find a new home free of gods and Chaos.

Final Fantasy Type-0/Agito
The souls of humans form the core of Arecia Al-Rashia and Gala's plan to open the Unseen Gate. While Arecia tries to use twelve chosen souls of exceptional strength to find and open the Gate, Gala uses his Lulusath Army to slaughter the people of Orience, wishing to cause a flood of souls to force the door open. Each time, both failed and events repeated themselves, as the land was locked in a stable time loop for the purposes of the experiment. The cycle of events is repeated 600,104,971 times before, the final time, Class Zero, the people chosen to try and force open Etro's Gate, alter the course of events and bring an end to the cycle. After their deaths, Arecia listens to their souls and decides to free Machina and Rem, two discarded members of Class Zero, from crystal stasis. Alongside this, she allows the people of Orience to remember their dead before finally abandoning the experiment. Their role in the story of Final Fantasy Agito is as yet unknown.

Final Fantasy XV
The souls of the dead play a crucial part in the story of Final Fantasy XV and its main character Noctis Lucis Caelum. According to a legend from the country of Tenebrae, whenever Etro opens the Unseen Gate, the souls of the dead ascend as a streak of light. Those who have a near-death experience see the light and receive magical powers from the Unseen Realm. Both Noctis and Stella Nox Fleuret bear magical powers, although the details behind any Focus they might bear or what other role souls play in the story are unknown.