Theseus had promised Aegeus to arrive with a white sail if he had been successful in his mission to save the Athenian youths in Crete. But Theseus forgot his promise and sailed by Cape Sounion with his usual black sails. Aegeus, anxiously watching, threw himself off the cliff in despair. The sea into which he leapt is called the Aegean Sea, in his honor, to this day. Theseus now became King of Athens.

Theseus was known as the greatest of Athenian kings. He fought against the Amazons and married the Amazon queen’s sister Antiope and with whom he had a son named Hippolytus. A great tragedy would occur later in Theseus’s life when his second wife, Phaedra, Ariadne’s sister, would attempt to seduce her stepson Hippolytus, and when Hippolytus refused to be corrupted, would falsely accuse him of trying to seduce her, thus causing Theseus to banish his own son and bring about his death.

Theseus joined his friend Pirithoüs in a fight against the half-man half-horse beings, the centaurs. He also joined him in an attempt to kidnap Persephone from the Underworld. This adventure failed and Theseus was trapped in Hades until Herakles managed to free him. Thus, like many heroes, Theseus experienced the process of death and the return to life.