Chaos

Chaos is not a person, but it's the beginning of this world. Greek philosofers have thought our to find a good theory (Thales of Milete and other philosofers). When the world was created there where two gods: Gaia (land) and Tartaros (underworld). Gaia created Ouranos (heaven) and Pontos (sea). The land (Gaia) married with the heaven (Ouranos) and they got 18 children: three Hecatoncheiren, three Cyclops and twelf Titans (six boys and six girls).
Ouranos got an oracle, that one of his twelf children would kill him. That's why Ouranos put all the born children in the Tartaros. Gaia hated Ouranos, since he put their kids in the Tartaros so she liberated her kids. Cronos one of the Gigants killed his farther and he became king of the gods.
Cronos married with Rhea, his sister. But Cronos get also an oracle: He will be defeated by one of his kids. So Cronos ate all his five kids (Hera, Demeter, Hestia, Hades and Poseidon). When his sixst child born, Rhea got a message of Gaia: Hide the child on Crete, because Cronos want to kill him. Zeus growed up and when he was a man he recovered his sisters and brother of the stomach of Cronos.
And the war started: The old gods against the new gods, the mountain Othrys against the Olympus. After ten years of war, Zeus recover the Hecatoncheiren and the Cyclops of the Tartaros. And Zeus won the war. He put the old gods in the Tartaros and he married with his sister Hera. They got four children: Hephaistos, Hebe, Ares and Hermes. Zeus got much more: Pallas Athena, Apollo, Artemis and many others. But also mortals: Heracles, Tantalos, Helena, Minos, Perseus and many others.