Demeter was one of the oldest deities in the Greek pantheon, she guaranteed the fertility of the earth and protected crops as well as vegetation. This close connection to the earth was inherited from her mother Rhea, and without a doubt, she was a local reincarnation of the earth mother goddesses commonly worshiped in rural communities during the Bronze Age. The sanctuary at Eleusis dedicated to the goddess and her daughter Persephone, as well as the Eleusinian mysteries practiced there, spread throughout the world of Archaic and Classical Greece, along with the idea that Demeter would protect her worshipers in the other life; to the Romans the goddess retained her popularity and was known as Ceres.
Daughter of Cronos and Rhea, sister of Zeus, Poseidon, Hades, Hera and Hestia, Demeter was the mother of Persephone and Iacus (both sons of Zeus) and Pluto (son of the mortal Cretan Iasion, who was later killed by lightning of jealous Zeus). She also adopted Demophon, the Eleusinian prince, who gave the human race the gifts of the plow and the knowledge of agriculture. Demeter was also chased by Poseidon and to escape his intentions, she turned into a mare; however Poseidon also became a horse and the resulting offspring was Arion, a winged horse ridden by Hercules. Demeter and Persephone very often appeared in pairs and were sometimes even identified as a single, dual-aspected goddess. The duo were frequently known as "the two goddesses" and as the Demeteres (two Demeters).
The most important mythology surrounding Demeter was the story of the abduction of her daughter Persephone (also known in Greek as Kore and Proserpina by the Romans) by Hades, the god of the underworld. One day Hades fell in love with Persephone as soon as he saw her, so she took her away in her carriage so that she would go and live with him in the underworld. In some versions, Zeus had given his consent to the abduction, the location of this crime being traditionally situated in Sicily (famous for its fertility) or in Asia. Desperate, Demeter searched all over the land for her lost daughter of hers and although Helios (or Hermes) told her the fate of her daughter, she continued to search for her until she finally reached Eleusis. It was there, disguised as an old woman, that the goddess cared for Demophon (or Triptolemus) the only son of Metanira, the wife of King Celeus, king of Eleusis. To reward the family for his kindness, Demeter wanted to make Demophon immortal by placing him in the fire every night. However, when Metanira saw this she was alarmed. In response, Demeter revealed her true identity and demanded that a temple be built in her honor. This was the beginning of the famous sanctuary of Eleusis in Attica.