Zodiark longeth to be made whole. For His restoration, for His resurrection, His servants labor without cease. They seek to tear down the barriers which surround the Source. Thus do they rejoice in their Ardor─in your calamities─for each marks a Rejoining. Seven times have they succeeded. Seven times hath the Darkness grown stronger. Seven times have I failed.The Word of the Mother, speaking for Hydaelyn
The Rejoining (also called Ardor or Calamity) is a recurring phenomenon in Final Fantasy XIV. Initiated by the Ascians, the Rejoining is an attempt to restore their god Zodiark's power, an act accompanied by cataclysmic turmoil that almost always destroys whole civilizations. These events are known as Umbral Eras to Eorzean historians, with the term Astral Eras referring to the periods of prosperity in-between these calamities.
Long ago, the ancient Ascians lived peacefully in the kingdom of Amaurot in a world where Light and Darkness existed as a single entity. An impending Calamity prompted the Ascians to create the dark primal Zodiark to save them. While the Calamity was averted, a faction of Ascians disapproved of Zodiark's presence and summoned the light primal Hydaelyn to keep him under control. It led to conflict between the two until Hydaelyn delivered the decisive blow that defeated Zodiark and sealed him. The force of her attack splintered the world into thirteen pieces, each reflections of the Source. Some of the very few survivors, as well as the new "human" species born from Zodiark, were caught in it, and as a result were fractured into a myriad of new mortal races with no memory of their original existence.
The Ascians that remained, forced to becoming incorporeal beings acting through vessels, seek to restore their world and Zodiark by shattering the barriers that separate a shard from the Source. Their first efforts ended in failure, flooding the thirteenth reflection with darkness and turning it into the void. The Ascians thus formulated a new method of Rejoining by causing a chaotic confluence of untold proportions with disastrous effects on civilization. These events came to be known as Umbral Calamities, each designed to reflect an element. The process involves placing a shard into a doomsday scenario that causes its elemental aether to leak into the Source and amplify the effects of a similar disaster, which the Ascians orchestrate to epic proportions; the resulting force causes the Source to completely absorb the ruined shard.
The Ascian Hades, referred to by his title Emet-Selch, would help a civilization develop as a tool for his kin. Among the civilizations he established was the Allagan civilization of the Third Astral Era, created to be decimated for the fourth Rejoining. Emet-Selch repeated this under the identity of Solus zos Galvus by setting up the Garlean Empire to set up the pieces for the seventh Rejoining. Though the primal Phoenix, fueled by prayers for a realm reborn, destroyed Bahamut midway through his apocalyptic rampage, it was not sufficient to halt the seventh Rejoining.
The periodicity of these calamities was noted by Sharlayan scholars, who developed a historical dating system based on the cycles of prosperity and ruin. These Umbral Eras were noted to be preceded by the sounding of the Echo. A group of scholars known as the Students of Baldesion of the Isle of Val study the Echo and its links to the Rejoining phenomenon. Sometime after the seventh Rejoining, the isle was destroyed under mysterious circumstances, the only known survivor being Krile. The isle is later revealed to have been displaced to another part of the world. Varis zos Galvus, the current emperor of Garlemald, reveals the Ascians' plan and the nature of the Rejoining to the Eorzean Alliance, whose leaders refuse his offer to help him make it happen.
The Ascians attempt another Rejoining in the form of an Eighth Umbral Calamity, caused by the Garleans' Black Rose arcane poison reducing Eorzea into a lifeless land from being amplified by the Flood of Light affecting the First. This would have plunged the world into an age of endless conflict, but the Scions of the Seventh Dawn work to restore the First while Zenos yae Galvus kills Emperor Varis, his father.
- In Final Fantasy XIV: Shadowbringers, Emet-Selch rants that in every calamity in every era, there was someone who fought against the Ascians.