Carbon is the common name for a metamorphic life form found during the Mage Wars. Carbons are enigmatic, mysterious beings, though common lore holds them to be artificial or magical in nature. Carbons are not "alive" in the conventional sense; they were made of carbon and silicon, highly ordered, and clearly intelligent; but no surviving examples have been studied with modern science. The beings very definitely existed (unlike some monsters of myth), but were all killed off. The last known sightings happened in the Second Chaotic Period; they are suspected to have been extinct by Eieber's lifetime.
The Carbon's true form is not known. They could take on any shape, but only mimic an existing shape (A Carbon was not capable of inventing a "new" form). They are believed to have been comprised of enchanted carbon and silicon. They grew by absorbing more of of those substances, and reproduced through asexual division.
A carbon could mimic any shape it or its progenitors encountered. They appeared to have infinite memory. While they reproduced by separating, they could also grow to essentially infinite size. To further evade detection, the Carbon could form a sort of matrix and hold additional materials within itself. Magical spells could not discern them from common objects. Carbons could be as large as a building, or larger if they felt so inclined.
Carbons are not alive in any conventional sense. They did not have cells, nor did they require oxygen or nutrients. A Carbon could be "killed" by inflicting significant damage on it, but they were known to be immune to "kill" spells devised by various mages. Since they were never alive to begin with, it's difficult to say that they have since become extinct.
They were made of very complex compounds comprised mainly of carbon and silicon.
The Gudersnipe Foundation has been open about its desire to capture and study a Carbon, and includes in its publicly accessible database the analysis of five samples held to be "carbon corpses". Many believe that the Foundation does in fact have living examples of Carbons in its inventory, and point to various technologies they believe were "carbon derived". A leading theory claims that Carbons provide the "real" control behind the Foundation's secretive "Simulator" technology.