Orphism is a mystery tradition of ancient Greece that emerged in the sixth century BCE around a set of poems and doctrines attributed to the mythical musician Orpheus. It broke from the mainstream Olympian religion in a specific way: where Homeric religion offered only the gray communal Hades for nearly all the dead, Orphism taught that the human soul was fundamentally divine, that it had fallen into the body from a higher state, and that through specific initiations, purifications, and knowledge it could return to its astral origin.
The Orphic myth of origin — preserved fragmentarily in the writings of later Neoplatonists and in the theogonies quoted by Plato, Proclus, and others — centers on the Titans' murder and consumption of the child Dionysus-Zagreus. Zeus destroyed the Titans with a thunderbolt, and from their ashes arose humanity. We are therefore a mixture: the Titanic body (earthly, corrupt) and the Dionysian spark (divine, immortal). The project of human life is to purify the body away and release the spark.
Orphic cosmology placed the soul's destiny among the stars. At death, the unpurified soul remained bound to the cycle of rebirth, transmigrating through plant, animal, and human bodies in an endlessly repeating circle. Gold tablets found in graves across Magna Graecia — Petelia, Thurii, Hipponion, and elsewhere — preserve the instructions the initiated were to follow. At the first spring in the underworld, the dead were to refuse the water of Mnemosyne-denying Lethe (forgetfulness) and instead drink from the cold water of Memory, and to say: I am a child of Earth and starry Sky, but my race is heavenly; you know this yourselves. Let me drink of the cold water flowing from the pool of Memory.
What follows for the properly initiated is ascent. The soul retraces its path through the planetary spheres it had descended through at birth, shedding at each sphere the passion or vice that had been accreted there: Mars shedding aggression, Venus shedding lust, the Moon shedding changeability, until at the outermost sphere it is the divine spark it had been before the fall, and it takes its place among the stars.
Orphic ethics followed the cosmology. Adherents were vegetarian (not eating the bodies of beings who might themselves be reincarnated souls), avoided wool (taken from an animal, it was unclean for burial), and practiced specific rituals of purification. The tradition influenced Pythagoras, who may have been influenced by Orphic sources, and through Pythagoras influenced Plato's myths of the soul in the Phaedo, the Phaedrus, and the final myth of Er in the Republic.
What distinguishes Orphism is that it was the first clear articulation, in the Greek world, of a moral afterlife with a genuinely cosmic stake. Your soul is a star that fell. Your life is the project of rising back. The body is not evil, but it is not you either; you are the spark within it, and you have forgotten yourself. The mysteries are the remembering.