Etro's gate

Etro's Gate, also known as the Unseen Gate, is a gateway to the afterlife in Fabula Nova Crystallis: Final Fantasy. It is referred to as Door of Souls (魂の扉) in the analects in Final Fantasy XIII and is operated by the goddess Etro. According to the official mythology, the universe is divided in two halves: the visible world, or the world of the living, and the Unseen World, or the world of the dead; and if the balance between the two worlds is broken, the universe would be in danger of collapsing.

XII. The Door of Souls
''When our earthly vessels meet their end, the souls they housed must leave this world. Would the path of their migration not be the same one as our departed gods? Must they not pass through the same doorway the Divine employed to reach that place that lies beyond?'' ''If this is the case, it stands to reason that, should a great many lives at once be cut short, a flood of souls would surge through the aforementioned portal. The Door would be thrown wide, and perhaps we might even glimpse the gleaming light of Divinity beyond.''
 * —On the Nature of Fal'Cie

XIII. Fabula Nova Crystallis
''Children of Hallowed Pulse scour earth, searching substance for the Door. Those of Fell Lindzei harvest souls, combing ether for the same. So have I seen.'' The Door, once shut, was locked away, with despair its secret key; sacrifice, the one hope of seeing it unsealed. When the twilight of the gods at last descends upon this world, what emerges from the unseeable expanse beyond that Door will be but music, and that devoid of words: the lamentations of the Goddess Etro, as She sobs Her song of grief.
 * —Author unknown

Story
Upon a person's death, what could be called their "soul", turns into crystal energy and passes through the gate to the afterlife. The fal'Cie, being machines, do not possess a soul and will never attain afterlife. The fal'Cie believe the Maker, the god who created the world of Final Fantasy XIII, has departed and gone beyond Etro's Gate somehow.

The fal'Cie devise a plan to send as much crystal energy through the gate as possible, by destroying Cocoon, believing the massive amount of deaths would force Etro's Gate wide open, and reunite them with their Maker back while world will be reborn. However, this act would destroy the balance of the world and Etro stopped the first attempt during the War of Transgression.

Lightning's group first hears of the plan from Cid Raines in Fifth Ark. Later, before ascending to Edenhall, the party can observe crystal energy glimmering in the air. They wonder of its significance, which is when Barthandelus appears to them in the guise of Galenth Dysley. He explains it means the Maker is soon to return, and as Barthandelus leaves and disappears inside the tower above Edenhall, Etro's Gate opens on the sky of Eden.



Later, after the party defeats Orphan, the lights of Cocoon go out, all but of the mysterious light that is Etro's Gate. As Ragnarok crystallizes the world of Cocoon, Etro uses her power to free the Pulse l'Cie of Cocoon from their fate before the gate completely closed.

The gate itself is only ever mentioned in the two final Analects, and in the battle theme "Born Anew", whose translated lyrics spell, "l'Cie, you promised to open the gate, full of eternal light!"

Final Fantasy XIII-2
After Lightning beats Caius Ballad and Chaos Bahamut, she sees the gate open above Valhalla. During this event, a man named Noel Kreiss falls towards Valhalla causing Lightning to go rescue him atop a summoned Bahamut. Upon picking up Noel, Chaos Bahamut breaks out of the rubble and pursues them.

Final Fantasy Versus XIII
Etro's Gate is the gateway to afterlife. Legend has it that upon a person's death, they will meet the goddess at the gate, who will open it and let the soul pass onto the afterlife. Etro is thus known as the Goddess of Death. Those who have had near-death experiences, may gain supernatural powers afterward.