In Greek mythology, Demeter (/diˈmiːtər/; Attic Δημήτηρ Dēmētēr. Doric Δαμάτηρ Dāmātēr) is the goddess of the harvest, who presided over grains, the fertility of the earth, and the seasons (personified by the Hours). Her common surnames are Sito (σίτος: wheat) as the giver of food or corn/grain and Thesmophoros (θεσμός, thesmos: divine order, unwritten law) as a mark of the civilized existence of agricultural society. Though Demeter is often described simply as the goddess of the harvest, she presided also over the sanctity of marriage, the sacred law, and the cycle of life and death. She and her daughter Persephone were the central figures of the Eleusinian Mysteries that predated the Olympian pantheon. In the Linear B Mycenean Greek tablets of circa 1400-1200 BC found at Pylos, the "two mistresses and the king" are identified with Demeter, Persephone and Poseidon. Her Roman equivalent is Ceres.
In some of the earliest accounts Demeter was triune goddess representing the Virgin (Kore), the Mother (Pluto "Abundance"), and the Crone ('Persephone the Destroyer'), representing the cycle of birth, life, and death. In later legends, the name Pluto was transferred to the god of the underworld, and elements of Kore and the name Persephone became associated as her daughter.
Another aspect of Demeter, was known as the Aganippe "the Mare who destroys mercifully", a black winged horse worshiped by certain cults. In this aspect her idols (such as one found in Mavrospelya, the Black Cave, in Phigalia) she was portrayed as mare-headed with a mane entwined with Gorgon Snakes. This aspect was also associated with Anion (or Arion) whom Heracles rode, who later inspired tales of Pegasus. Aganippe became associated with a spring, where Pegasus was born according to one legend, and the nymph of the same name.
Demeter as an agricultural goddess appears rarely in the epic poetry. In Homer's Odyssey she is the blond-haired goddess who is separating the chaff from the grain. The harvesters must pray to Zeus-Chthonios (chthonic Zeus) and Demeter so that the crop will be full and strong. In the Theogony of Hesiod she is the daughter of Cronus and Rhea. At the marriage of Cadmus and Harmonia, Demeter lured Iasion away from the other revelers. They proceeded to have intercourse in a ploughed furrow in Crete; she later gave him a son, Ploutos.
Persephone, Queen of the underworld, is daughter of Zeus and Demeter. The myth of the rape of Persephone seems to be pre-Greek. In the Greek version Ploutos (πλούτος, wealth) represents the wealth of the corn that was stored in underground silos or ceramic jars (pithoi). Similar subterranean pithoi were used in ancient times for funerary practices and Pluto is fused with Hades, the King of the underworld. During summer months the Greek Corn-Maiden (Kore) is lying in the corn of the underground silos, abducted by Hades (Pluto) as it is described in Theogony. Kore is fused with Persephone, the Queen of the underworld. At the beginning of the autumn, when the corn of the old crop is laid on the fields she ascends and is reunited with her mother Demeter, for at this time the old crop and the new meet each other.
In the myths of isolated Arcadia in southern Greece Despoina (Persephone), is daughter of Demeter and Poseidon Hippios, Horse-Poseidon. These myths seem to be connected with the first Greek-speaking people who came from the north during the Bronze age. Poseidon represents the river spirit of the underworld and he appears as a horse as it often happens in northern-European folklore. He pursues the mare-Demeter and she bears one daughter who obviously originally had the form or the shape of a mare too. Demeter and Despoina were closely connected with the springs and the animals. They were related with the God of the waters Poseidon and especially with the mistress of the animals Artemis who was the first nymph.
In another tale, Demeter punished Erysichthon of Thessaly by inflicting him with insatiable hunger after he cut down a tree in a sacred garden which killed a dryad and the other dryads informed Demeter of this.