Sokrates on Iakkhos, the Underworld, Dionysos and Reincarnation

Sokrates : But now, since the soul is seen to be immortal, it cannot escape from evil or be saved in any other way than by becoming as good and wise as possible. For the soul takes with it to the other world nothing but its education and nurture, and these are said to benefit or injure the departed greatly from the very beginning of his journey thither. And so it is said that after death, the tutelary daimon of each person, to whom he had been allotted in life, leads him to a place where the dead are gathered together (i.e. the daimon guide is Plato's equivalent of Hermes, guide of the dead); then they are judged and depart to the other world with the guide whose task it is to conduct thither those who come from this world, probably Iakkhos; and when they have there received their due and remained through the time appointed, another guide, probably Dionysos, brings them back after many long periods of time (i.e. they are reincarnated).

Plato, Phaedo 107c ff