In Greek mythology, Polydorus (Ancient Greek: Πολύδωρος, "many-gifted") was a king of Thebes, the youngest and only male child of Cadmus and Harmonia. By Nycteïs he fathered Labdacus, ancestor of the Labdacids. He succeeded Pentheus after Dionysus' vengeance on the house of Agave, then died while Labdacus was still young, leaving Nycteus as regent. Distinct from Priam's son Polydorus of Troy.
Adapted from Wikipedia, "Polydorus (son of Cadmus)" · CC BY-SA 4.0
I.Family
Polydorus was the youngest and only male child of Cadmus and Harmonia; his sisters were Autonoë, Ino, Agave, and Semele. By Nycteïs, daughter of Nycteus, he was the father of Labdacus.
II.Mythology
Upon Cadmus' death, Pentheus — son of Echion and Agave — banished Polydorus and ruled Thebes briefly until Dionysus prompted Agave to kill him. Polydorus then succeeded as king and married Nycteïs. When Labdacus was still young, Polydorus died of unknown causes, entrusting his father-in-law Nycteus as regent for the infant prince.
In Pausanias, Polydorus' rule began when Cadmus abdicated and migrated with Harmonia to the Illyrian Enchelii — a timeline unique to that source. Pausanias also says that with the thunderbolt that struck Semele's bridal chamber there fell a log from heaven, which Polydorus adorned with bronze and called Dionysus Cadmus.
III.Homonym caution
This Theban Polydorus must not be confused with Polydorus son of Priam, the Trojan prince slain in the aftermath of Troy's fall.