"Avenged we not on Theseus his assault!"

(Canto 9, line 54)

Theseus, one of the foremost heroes of the Greek pantheon, was one of the Argonauts participating in Jason's hunt for the golden fleece. Among other deeds, he killed the bull-headed Minotaur, abducted the Amazon queen Hippolyta and became the king of Athens. Together with his friend Pirithous, prince of the Lapiths, he descended into the Underworld to abduct its queen Persephone. However, in the underworld, they became magically fixed to rocks and could not escape. Theseus was later rescued by Hercules. Apparently, the Furies think that if they had punished Theseus properly, people would not, like Dante, come down to the Underworld of their own accords.