A mother’s hands
The story of Agave is the story of a single act, and the act is a killing. She is one of four daughters of Cadmus and Harmonia at Thebes — Autonoe, Ino, Semele and Agave — and she is married to Echion, one of the sown men who grew from the serpent’s teeth Cadmus planted. Her son is Pentheus, and by the time Dionysus comes to Thebes, Pentheus holds the kingdom.
Dionysus forces the women of Thebes out of their houses and onto Cithaeron, to revel in Bacchic frenzy. Pentheus inherits his grandfather’s city and tries to stop what is happening. Apollodorus gives the killing in one sentence:
Πενθεὺς δὲ γεννηθεὶς ἐξ Ἀγαυῆς Ἐχίονι, παρὰ Κάδμου εἰληφὼς τὴν βασιλείαν, διεκώλυε ταῦτα γίνεσθαι, καὶ παραγενόμενος εἰς Κιθαιρῶνα τῶν Βακχῶν κατάσκοπος ὑπὸ τῆς μητρὸς Ἀγαυῆς κατὰ μανίαν ἐμελίσθη· ἐνόμισε γὰρ αὐτὸν θηρίον εἶναι
“Pentheus, whom Agave bore to Echion, had succeeded Cadmus in the kingdom, and he attempted to put a stop to these proceedings. And coming to Cithaeron to spy on the Bacchanals, he was torn limb from limb by his mother Agave in a fit of madness; for she thought he was a wild beast.” — Apollodorus, Bibliotheke 3.5.2, tr. J. G. Frazer
The Greek is spare. He comes to Cithaeron as a spy, τῶν Βακχῶν κατάσκοπος, and his mother tears him apart κατὰ μανίαν, in madness. The verb ἐμελίσθη, dismembered, puts the act in the passive: the agent is ὑπὸ τῆς μητρὸς Ἀγαυῆς, by his mother Agave. Then the reason, in two words: ἐνόμισε γὰρ αὐτὸν θηρίον εἶναι, she thought he was a wild beast. Nothing in that sentence names what beast. She sees her own son on the mountain, and what she sees is an animal to be hunted.
A god proven
The sentence that follows belongs to Dionysus, not to Agave. Having shown the Thebans that he was a god, δείξας δὲ Θηβαίοις ὅτι θεός ἐστιν, he goes on to Argos. The death of Pentheus is the proof. The women of Thebes were made to abandon their houses and revel on Cithaeron; the king who tried to stop them is killed by one of them; the god’s power is established. What Agave believes she is doing — killing a beast — and what she is actually doing — killing her son — run parallel and never meet. The madness is not a punishment for anything she did. It is the instrument by which the god demonstrates his divinity to a city that doubted it.
Agave is named in the relations of three other entries: Cadmus lists her among his children, and Ino and Semele name her as a sister. She is not filed as a goddess, because she is not one. She is the mother of the king and the daughter of the founder, and she appears in the story only to kill.