The lord general of the monstrous forces invading Palamecia. No one knows either the intent or the cause for Chaos's invasion. He only seems interested in destroying all that stands in his path. While it is prophesied that the Warrior of Light will defeat him, no one knows when this will occur, or if it will happen at all.
—In-game Glossary entry
Chaos is "the formless matter supposed to have existed before the creation of the universe."