There are two interesting design choices in Final Fantasy VIII that ground claims about its mythos and the rules that govern its fictional universe: first, that the visual presentation and narrative tenor strives to be as realistic as possible; and second, that they made the creation myth of the world entirely miss-able. One of your first opportunities occurs in that sleepy seaside town beside the protagonist's military academy, Balamb town, where an old man lectures his grandson:

Long, long ago...

When this world was just made, there was a strong god called 'Hyne'. This god was very, very strong, but after fighting a lot of monsters, he became very tired. So he made 'people' like you and me to do all the work, and the god went to sleep.

However, the god was very surprised when he awoke. Surprised that there were so many people. Hyne decided to reduce the number of people by taking away the children.

Of course, everyone was scared then, too. And so, the battle against Hyne began. Even though the people were small, they all got together, and finally cornered him. Hyne didn't know what to do. Out of desperation, he gave half of his body to the people and ran off with the remaining other half. Well, he was a god. Anyway, it turns out Hyne tricked the people. The half that Hyne ran away with was the half that had the stronger magic. Hmmm... It might be close by, actually. It might even be watching you.

OLD MAN IN BALAMB TOWN

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There are a few variations on this story, and a few morsels that connect it to the rise of the sorceresses. The Balamb Garden informational panel (the same place you can nab Shiva and Quetzalcoatl, your earliest Guardian Forces) includes a casual mention of Hyne as a time frame for when the sorceresses began to appear, though possibly saying 'since the time of Hyne' is the FFVIII equivalent of since time immemorial. The only other available in-game creation explanation takes place aboard the white SeeD ship that escorts Ellone around the globe; the primary difference involves the introduction of a human protagonist and a war over Hyne's body, which, in this version, turns out to be completely inert, a last deceit by their god. The Final Fantasy VIII Ultimania Omega guide essentially follows those elaborations, but also includes an explicit causal connection between the body of Hyne and the magicality of the sorceresses:

However, the other half of Hyne's body was nowhere to be found. The humans began referring to the missing "Hyne" as "Hyne the Magician", and sought him for generations. It's to be expected that the "magic of Hyne" could not be found. Because of people's feelings at that time, it concealed itself in bodies, in the form of women, people who it was thought should be protected.

THE LIFESTREAM.NET TRANSLATION

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I find it fascinating that at the heart of FFVIII lie hidden binds between gender and magic and a god who does not love humanity - buried beneath a story that looks superficially modern, even futuristic, space-ships, time travel, locomotives, vying nation-states scattered across a barren globe that hire child soldiers. It is also a love story, between a mercenary and politician's daughter, between an orphaned boy and a magical girl. The game centers on the ways that they save each other, all the while facing one consistent villain in various guises: Ultimecia, a sorceress from the future who does not want to die, who wants to be alone forever.

I'm going to speculate on the nature of this myth and what fruit it bears when trying to think about how magic works, how sorceresses are related to the monsters of the world, but first I want to call attention to an interestingly similar creation story.

Plato's Symposium involves several big-name figures from Ancient Greece competing in dramatic oratory (as one does), each speaking on the nature of love. Aristophanes connects it to an ancient creation myth. Initially each human being was a conjoined set of two: the children of sun, two men together; the children of the earth, two women together; and the children of the moon, a man and a woman each. They began to try to climb mount Olympus, to rival the gods, but Zeus struck each pair with a thunderbolt to separate them; thus love is really a search for a missing half. Hedwig and the Angry Inch put it best:

Folks roamed the earth
Like big rolling kegs
They had two sets of arms
They had two sets of legs
They had two faces peering
Out of one giant head
So they could watch all around them
As they talked while they read
And they never knew nothing of love
It was before the Origin of Love...
Last time I saw you
We had just split in two
You were looking at me
I was looking at you
You had a way so familiar
But I could not recognize
Cause you had blood on your face
I had blood in my eyes
But I could swear by your expression
That the pain down in your soul
Was the same as the one down in mine
That's the pain
Cuts a straight line
Down through the heart
We called it love
So we wrapped our arms around each other
Trying to shove ourselves back together
We were making love

ORIGIN OF LOVE

hedwig and the angry inch

Like the story of Great Hyne, this is a myth of human hubris, but in FFVIII, humanity bests their god, who then bisects himself in order to escape. The spoils of that victory are debatable, but it is still not a loss. And yet, if one version of Hyne's legend is to be believed, it still leads to a difference in the sexes: sorceresses are women who wield magic through a connection to Hyne's discarded body, allegedly from that body's desire to protect them.