The Apocalypse is an event in Lightning Returns: Final Fantasy XIII that refers to the inevitable death of the world of Nova Chrysalia. "Apocalypse" was used on the game's official site before it got merged into Square Enix's site, but Nova Chrysalians tend to refer to the approaching event as the "end of the world".
Due to Nova Chrysalia's instability brought about by the merging of Gran Pulse and Valhalla, a chain reaction will occur when the planet goes supernova and collapses into a black hole that sucks in the Chaos and anything else within its gravity to create a new unseen realm, that will serve the role Valhalla once did as a middle world between life and death. As the savior with thirteen days to fulfill her mission, Lightning must gather enough Eradia from saved souls to give to the world tree Yggdrasil to prolong the world's lifespan.
Once the bells toll to the end of the final day, and the god Bhunivelze is defeated, the Apocalypse begins and consumes everything in its wake, including the deity's crystallized form. With the exception of her last incarnation, the incarnations of Paddra Nsu-Yeul remain behind to become the new goddesses of death to act as the keepers of balance between the new unseen realm and the new world in the late Etro's stead, with Caius Ballad staying with her. The final Yeul joins Noel and the rest of humanity as their souls travel to the new world to begin their lives anew.
Etymology and symbolism
Apocalypse (Ancient Greek: ἀποκάλυψις apokálypsis, from ἀπό and καλύπτω meaning "uncovering"), translated literally from Greek, is a disclosure of knowledge, i.e., a lifting of the veil or revelation. In religious contexts it is usually a disclosure of something hidden. Today, it is commonly used in reference to any prophetic revelation or so-called end time scenario, or to the end of the world in general.
Various Lightning Returns: Final Fantasy XIII aspects are based on Norse mythology. As alluded to in Final Fantasy XIII, the world will end in a great battle called Ragnarok, killing numerous gods, triggering many natural disasters, and a globe-spanning world war. After Ragnarok the world will be reborn, and the surviving gods and mortals will join to rebuild civilization in the new world.