The Black Materia

[Sephiroth]

The Black Materia was a gift from the Planet itself. The Cetra normally didn't need any Materia to summon magic but it was already a Materia when they got it. And yet they knew it was to powerful to use it and so they just sealed it away. Materia is just an explanation for how to use the power of the planet. Then body and mind react to that materia and you summon the spell. Other than people like the Cetra or Sephiroth - of course later Sephiroth was able to summon magic without Materia and the Black Materia itself was there for a plot, not to mention, that it was a sealed magic and although he absorbed the knowledge about Meteor in the lifestream he obviously couldn't find a Cetra who knew how to summon Meteor, because it was a sealed magic, but this is all just to have a plot - who can use magic without materia because of their knowledge about how to use the planet's power and their enormously strong will.

Seeing the pictures on the wall of the temple of the Cetra I often thought about if the Cetra maybe used the Black Materia and - accidentaly, of course they didn't know it - summoned JENOVA with it, so the Meteor on the wall would be JENOVA. And after that they have sealed it away because of the dangerous possibilities this materia brings with it.

This part of the story would have been cool to be told this way. But unfortunately it was not.

The Cetra were definitely bound on Gaia. They were not able to travel through space. Not on Meteor either. The Cetra were just human beings with supernatural abilities, but still the ancestors of the human race.

About the White Materia - well, Final Fantasy is always a good VS evil story, so it was normal to bring in Holy. Aerith and Sephiroth really represent the absolute good and evil parts. You can also say "The good and evil part of the planet/lifestream itself", so having the "white", innocent and pure Materia which is also called "Holy" which stands for protection and having the "black", light-absorbing and tainted Materia which is called "Meteor" and stands for nothing but pure destruction - so death (Meteor/Sephiroth), which is bad for life (Holy/Aerith and all the others) because they don't even have a chance to live and not to mention the fact that it is even more showed how ridiculous their battle against Sephiroth is when he just blocks Holy, is all part of telling a wonderful story with a very easy thought - the thought about a battle between good/life and evil/death.

You may not forget that really both magics were sealed. The knowledge how to summon Meteor was sealed inside the Black Materia which existed as the temple of the Ancients. And the knowledge of how to use the White Materia which would summon Holy in the end was sealed in the City of the Ancients.

Of course there is no explanation why the White Materia does also exist. But the planet obviously created it thinking someday a being - Sephiroth - could use Meteor for his own purpose. And yes, the question "Why did Gaia create the Black Materia?" cannot be answered because there is no actual answer. It wouldn't even need the Black Materia to die by its own purpose now that the story of Omega WEAPON and soul harvester Chaos exists in the world of Final Fantasy VII.