Dionysus is the god of wine and madness, vegetation, and the theatre, and was the focus of various mystery cults.
He also shakes things up when it gets dull.
Dionysus is represented by city religions as the protector of those who do not belong to conventional society and thus symbolizes everything which is chaotic, dangerous and unexpected, everything which escapes human reason and which can only be attributed to the unforeseeable action of the gods.
Dionysus made a habit of stealing the identities of his worshippers; the bacchants dancing on the mountainside have no separate personalities; they are mad, crazed, they have been taken over by the god; and they are all alike.