A few bits from a paper I just wrote on Euripides' Bacchae. Maybe you'll be interested.
Commentators have remarked on Pentheus’s early interest in Dionysian ritual, even as he voices opposition to Dionysus and imprisons the Maenads. This conflict makes sense if we understand Pentheus’s relationship to the history of the city. Cadmus, the founder of Thebes, killed a dragon and scattered its teeth into the earth. Echion, Pentheus's father, was born from the teeth, so Pentheus is, in a manner of speaking, part dragon. But Pentheus's mother, Agave, is the daughter of Cadmus Dragon-killer. Half-dragon, half-dragonslayer -- Pentheus is a divided man. In reality, Pentheus has always been part-Dionysian, which is why he succumbs to Dionysus. Peter Leithart notes that the temptation “only works . . . because Pentheus is already inclined to follow Dionysus’ instructions.” And Pentheus’s tendencies are forshadowed in the epithet “dragon-born.”
One passage that seems unfair is the curse pronounced on Cadmus at the end of the play. Dionysus praises Cadmus at the beginning of the play for making a shrine to Semele; Cadmus has been telling the city that Dionysus is indeed the son of Zeus, and Cadmus is one of the few men in the city to acknowledge him as a god. By normal standards, Cadmus has been faithful to his grandson the god. But he must be punished for two reasons. First, he is still the dragon-killer. Fundamentally, he is still opposed to the gods, and he is responsible in a way for his grandson: the messenger who relates Pentheus’s death arrives mourning, “This house founded by Cadmus, the stranger from Sidon who sowed the dragon seed in the land of the snake.”
In addition, Cadmus’s transformation into a snake represents the fate of the city itself. As founder of Thebes, Cadmus can be seen as a type of the whole city, and at the end of the story Dionysus reigns in the city. Thebes has become a Dionysian, and Cadmus has become the god’s symbol. But Cadmus is now more than a symbol – in a manner reminiscent of Oddyseus’ penance as an “evangelist” of Poseidon, Cadmus is sent out into the world to continue Dionysus’ work. He will lead barbarians, easterners like Dionysus himself, into Greece – and he will bring them in war (Ares’ domain, now usurped by Dionysus).