The Black Materia (黒マテリア, Kuro Materia?) is a mysterious and incredibly powerful Materia, as well as one of the oldest, having existed since the time of Jenova and the Ancients in Final Fantasy VII. It and its counterpart, the White Materia, are the two unique Materia, there being only one of each. It is used to summon the "Ultimate Destructive Magic", Meteor, which has the power to destroy the entire Planet. Few know of its existence, let alone how to use it.
After Sephiroth fell into the Lifestream following the Nibelheim Incident, he concocted his plan for world domination. Immersed in the Lifestream, he learned of the Black Materia and schemed to use it to summon a Meteor upon the Planet and absorb the Lifestream's energy as it would rush to heal the Planet, ascending to godhood.
Upon learning Sephiroth is seeking the Black Materia, the party rushes to the Temple of the Ancients to try to stop Sephiroth from obtaining it. They discover the temple itself is the Materia, transfigured by the Ancients. It can only be transformed into Materia by solving its puzzles but the person attempting to obtain the Materia would be crushed within the Black Materia as a final defense against any evil trying to use it.
Cait Sith offers to use his mechanical body to solve the puzzles. Unlocking the Black Materia, he is destroyed but a second Cait Sith arrives to take his place. Cloud retrieves the Black Materia from the hole left in the temple's place, but Sephiroth bends his will through the Jenova cells in Cloud's body and forces Cloud to pass it over to his control.
After defeating Jenova∙DEATH in Whirlwind Maze, the party reclaims the Black Materia. Cloud can entrust it to either Barret Wallace or Red XIII, although no matter whom he gives it to, Sephiroth tricks the holder into returning it to Cloud who delivers it to Sephiroth's true form resting in a Materia cocoon within the Northern Cave. Sephiroth uses it to summon Meteor before the Weapons awaken, and the Materia is never heard of again.
As its name suggests, the Black Materia is dark, appearing purple, blue, or black depending on the light. The Materia is large enough to fill the holder's palm.
In its transfigured form as the Temple of the Ancients it is in the shape of a ziggurat (step pyramid), with its entrance at the top of a long staircase in a manner similar to the pyramids of the Aztecs. Within it are several passages, some of which have carved murals.
The Black Materia is the strongest known Materia. Sephiroth can only utilize its power among the abundance of Lifestream energy at the Northern Cave.
These stones, developed by the ancient Saronians, are the result of experiments in storing knowledge within gems for later generations. They are said to enhance the abilities of the possessor.
Because of its ties to Sephiroth, the Black Materia has been released in merchandise as an item related to him, and is the focus of several Final Fantasy pendants and keychains.
Materia means "matter" or "substance" in Latin. It also means "subject" or "matter" in Italian, Spanish, and Portuguese.