Etro's gate

The Door of Souls is a gateway to the afterlife in Fabula Nova Crystallis: Final Fantasy XIII. It is operated by the goddess Etro.

Final Fantasy XIII

 * 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

Upon a person's death, what could be called their "soul", turns into crystal energy and passes through the Door to the afterlife. The fal'Cie, being machines, do not possess a soul and will never attain afterlife, of which they greatly envy the humans. The fal'Cie believe the Maker, the god who created the world, has departed and gone beyond the Door of Soul, a way the fal'Cie may never follow.

The fal'Cie devise a plan to send as much crystal energy through the Door as possible, by destroying Cocoon, believing it will throw its door wide open, and allow them a glimpse of their missing deity. By opening the Door the fal'Cie believe they can call the Maker back into the world and the world will be reborn.

The party first hear 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, the camera shows a sight of a portal of light opening on the sky of Eden. It is unclear whether this is supposed to represent the Door.

The Door itself is only ever mentioned in the final analect unlocked in the datalog upon defeating all 64 missions.

Final Fantasy Versus XIII
The Door of Souls is the gateway to afterlife operated by the goddess Etro. Legend has it that upon a person's death, they will meet the goddess at the door, who will open it and let the soul pass onto the afterlife. Etro is thus known as the Goddess of Death.