Dionysus or Bacchus is the god of the grape harvest, winemaking and wine, of ritual madness, fertility, theatre and religious ecstasy in ancient Greek and Roman religion and myth. His worship became firmly established in the seventh century BC. He may have been worshipped as early as c. 1500–1100 BC by Mycenean Greeks; traces of Dionysian-type cult have also been found in ancient Minoan Crete. His origins are uncertain, and his cults took many forms; some are described by ancient sources as Thracian, others as Greek. In some cults, he arrives from the east, as an Asiatic foreigner; in others, from Ethiopia in the South. He is a god of epiphany, "the god that comes", and his "foreignness" as an arriving outsider-god may be inherent and essential to his cults. He is a major, popular figure of Greek mythology and religion, becoming increasingly important over time, and included in some lists of the twelve Olympians, as the last of their number, and the only god born from a mortal mother. His festivals were the driving force behind the development of Greek theatre.