Gaia, Ge, Tellus [Roman], Terra [Roman]
Gaea, or as she is otherwise known, Mother Earth, is the cradle of creation. Herself created from Chaos, she went on to give birth to Uranus and Pontus; the earth creating the sky and the sea. By Pontus she gave birth to Nereus, and by Uranus she gave birth to the Titans, the Cyclopes, and the Hecatoncheires.
Uranus resented his children, so their mother hid them within herself, deep in the earth. She then proceeded to fashion a large iron sickle with which Cronos, the youngest of the Titans, attacked his father. From some of the blood spilled, Gaea created the Gigantes, the Erinyes and the Harpies.
Because she is so integrated with the earth, Gaea was often invoked in prayers when the underworld was involved.