Final Fantasy III is an old game.

Like most old games back in the day, this means that most of the background information and lore was confined to guidebooks or magazines or what have you. Very rarely was any of this info ever brought over westward, with the guides and whatnot removing it. And if the game in question never released in the west...

At the time of this writing, I do not have these materials nor the means of which to read them. My info instead comes second-hand, as a JP wiki does make mentions of the info and JP twitter users also occasionally discuss these faccets. For those who wish to verify or help, the guides in question are NTT publishing guides. At least two of the guides are floating online, but neither of them have been translated and the one that has most/all of the lore doesn't seem to among those.

Meanwhile, the 3D remake had its own minor set of additions and changes to the lore... most of which is hidden in the unused text...

The Sasune/Saronia War

Magic in the FF3 world had a surprising origin.

At some point in time, Doga gave humanity the gift of magic. Humanity used magic in various ways to aid in living or for religious purposes. Magic in those days did not have specific designations; It was all simply magic.

At some point, however, Sasune went to war with Saronia. While the countries started off as relatively evenly matched, Sasune started to research Doga's magic. They eventually found means to push the magic further, creating more destructive spells in what would be known as Black Magic.

However, not all of the mages were onboard with such a destructive use for magic. They promptly went AWOL and went to Saronia. Eventually, Saronia began to experiment with magic as well, resulting in the creation of what would be known as White Magic.

Both kingdoms continued to refine their magic, pushing it further and further as a sort of magical arms race. In the end, they created the pinnacles of Black and White Magic: Flare for Black Magic and Holy for White Magic. When they attempted to deploy the spells however, they collided, wiping out tens of thousands of soldiers. The war ended shortly afterwards and the spells were sealed within Eureka.

It is said that the Red Mage, which would become a staple of Sasune later, uses the magic that existed prior to Sasune's experimentation.

Holy & Flare

Both spells have definitions in the guides explaining how they work:

Holy: Uses the caster's life energy without abandon to blast the opponent. Is classified as White Magic due to using life energy.

Flare: Gather's antimatter from another dimension and fires it at an opponent. It is intended to destroy a target at the atomic level and is powerful enough to destroy a continent if used correctly.

The Wrath Of Light

Or "The Time When Light Was Bad, Actually"

In the times of old, the Ancients grew arrogant. In their arrogance, they decided that there was no risk in only using the Light and modeled their society around it.

But there was.

By unsettling the equalibrium, the Ancients unwittingly unleashed a Flood of Light which threatened to destroy the entire world. Meanwhile, in the World of Darkness, the Dark Crystals chose four warriors to become the Warriors of the Dark. The Dark Warriors would eventually travel to the World of Light and confront the Cloud of Darkness, defeating it and saving both a great cost.

The Wrath of Light is a pure background element and, this being a Famicom-era game, the game itself gives no proper explanation to it. What's known is that the ancients made an oopsie, the Warriors of Darkness had to clean up their mess and that Owen cryogenically froze Desch so that he could protect the Tower of Owen in case something happened [1].

The remake adds slightly to the nature of the Flood of Light, mostly due to expanding upon the nature of Xande's Flood of Darkness. The Flood of Darkness is said to have cut the world off from the sun, creating an eternal night and causing time to stop. The implication is that the Flood of Light did the same thing: The Ancients created an eternal day and it threatened to freeze time entirely.

The unused text of the remake heavily implies that this was indeed the case, but adds a further wrinkle onto the story; There's an implied connection between the Earth and the Sun in the FF3 remake. This is primarily mentioned by the Warriors of Darkness, but Desch and Doga both explain it more properly. In particular, all three mention an odd quirk: Prior to the Flood of Light, the Sun used to revolve around the Earth. During the Flood, the Sun stopped moving. After the Warriors of Darkness saved the World, the Earth now revolves around the Sun.

The concept of a "Flood of Light" was also used in Final Fantasy XIV's "Shadowbringers" expansion. However, it lacks the timestop/"Earth and the Sun" elements, leading to a different interpretation. Notably, while there is no sign of the world having been scarred by the Flood of Light in III, XIV's the First was reduced to a single region due to all other places being erased by the Flood.


[1]: Even then, the remake recontextualizes this by having Desch be frozen long after the Flood of Light.