What is exactly the "void" and where does it come from?

[Anonymoose]

The void is a place where a lot of fanon comes from, as well. /s

Let's start with...

CONFIRMED TRUTH AS OF 3.45 [SPOILERS]

For ages, Eorzeans have believed in a dark realm that exists beyond the corporeal world. According to these beliefs, the void is not one of the Seven Heavens (where the Twelve retreated after the First Umbral Era) or the Seven Hells (that came into being as a byproduct of the Seven Heavens, home to the once-mentioned-ever Black Warden). Belief in the void is spurred by the appearance of entities that Eorzeans believe are too strange to be natural; it is believed that these entities were sent to wreak havoc on Eorzea by some sinister force, thus the biological classification "voidsent".

Unfortunately for naturalists and scholars everywhere, these beliefs are not always accurate. Eorzeans have classified several beings that are natural as voidsent (and probably vice versa; some voidsent have likely had their true nature escape notice). You can only trust NPCs and system text to a certain degree. You are encouraged to become a naturalist yourself and argue with your fellow scholars until the game gives you something better to go by.

That said, the void is real.

When Hydaelyn (the Will of Light-with-a-capital-L) expelled Zodiark (the Will of Darkness-with-a-capital-D) from the aetherial sea and sealed him within a moon, it stressed the fabric of reality so hard that it cracked, causing thirteen reflections of our primordial world to fan out in all directions. The goal of the Ascians is to throw these reflected worlds into just enough chaos that the boundaries between them and the original world break down. When this happens, the entire reflection is destroyed, everything there dies, and all of the aether is funneled back into the sea. The Ascians believe that this will heal the universe and that it is integral to the second coming of Zodiark, their "one true god".

When Igeyorhm attempted to throw the Thirteenth reflection into chaos, it went awry. The world's balance was already tipped towards Darkness-with-a-capital-D, and she easily crushed the inexperienced Warriors of Light that Hydaelyn called to defend it. Rather than teetering on the brink until the world was Rejoined, equilibrium was lost, unleashing a Flood of Darkness and sheared all aether from that world (a Flood of Light would have done the same). All life that existed in that plane could no longer know life or death, and atrophied into aether-starved monstrosities that have vied for dominion over the twisted realm ever since.

The boundaries between the void and our world are constantly in flux. Sometimes, this results in very small naturally-occuring rifts in our world through which low-ranked voidsent are able to slip through. These entities are likely the inspiration for (and confirmation of) Eorzean belief in the void, even if they understand it well. There are two methods for a more powerful voidsent to enter our world. One is that the boundary is forcibly torn wide open by something such as a powerful magick. Holding the voidgate open long enough for a voidsent to manifest requires a lot of power and aether. The other method is to open a small gate through which only the voidsent's essence passes quickly through and into a prepared vessel. The latter case may be easier, but the vessel can't be too weak to contain the voidsent (and the voidsent's power is thus also limited by the vessel).

THEORYCRAFT, HEADCANON, AND FANON AS OF DECEMBER 2016

Hydaelyn is often referred to as the will of Light (capital L), and Zodiark the will of Darkness (capital D). Both Light and Darkness appear to be aetherial. For example, the Chrysalis is made entirely of Dark crystal. Lower-case light and darkness are mentioned constantly, but seem to be a bit poetic, referring to aether or a vacuumous lack thereof. Our world is a world of light because it is saturated with aether. The darkness of the void, starved of aether, comes to consume that light. Thus the Cloud of Darkness is likely just a cloud of darkness, capitalized because that's what you do to proper nouns.

Some believe that there is a Void-with-a-capital-V that exists beyond the aether-vacuumous realm of monsters left where the Thirteenth reflection once was. This Void is thought to be a swirling eternity of formless chaos. Such a belief fits with the cosmology of other Final Fantasies, especially if you start to get into crossovers like DISSIDIA. We know that Eorzeans believe that the Twelve came into being from such a formless chaos, but it is known only as "The Whorl" (no relation to Leviathan (probably...)). So far, there has never been a mention of Void-with-a-capital-V in Final Fantasy XIV. Like the Cloud of Darkness, it appears only in proper nouns such as the names of attacks (e.g. Void Fire).

Some believe that a void born from Light instead of Darkness would have different properties, as the Warrior of Darkness stated that it left only "blank perfection" in its wake. Rather than monstrosities, there would be nothing. We can't be sure of this, as Urianger specifically said that if the world the Warriors of Darkness came from (the First) fell to light, every being there would be trapped in a world without life or death. That sounds just like the void that is the Thirteeth. Void might just be void, no matter how it's born. Nevertheless, it doesn't seem to matter; no lightborn void is known to exist (yet).

The Ascians really don't seem to be on the same page. The fourteen overlords (black robes) seem to be possessed of Zodiark's hate and greed. They bicker and disagree and vie for power amongst one another while trying to interrupt everything even remotely related to the Light. Lahabrea yells about Hydaelyn needing to be burned out of existence. Nabriales bids the void to entirely consume the Source (original world from which the others were reflected). Meanwhile. Elidibus says he just wants to make things right and restore everything to how it was before Hydaelyn and Zodiark were divided; he will even assist the Light against the Dark if it keeps things balanced enough to stop a Flood; Zodiark needs that aether and has no use for void. (Granted, a world without Hydaelyn and Light probably still means an end to Life as we know it.)