Orphism (more rarely Orphicism) (Ancient Greek: Ὀρφικά) is the name given to a set of religious beliefs and practices in the ancient Greek and the Hellenistic world, as well as by the Thracians, associated with literature ascribed to the mythical poet Orpheus, who descended into Hades and returned. Orphics also revered Persephone (who annually descended into Hades for a season and then returned) and Dionysus or Bacchus (who also descended into Hades and returned). Orpheus was said to have invented the Mysteries of Dionysus. Poetry containing distinctly Orphic beliefs has been traced back to the 6th century BCE or at least 5th century BCE, and graffiti of the 5th century BCE apparently refers to "Orphics".