Theseus Fighting the Crommyonian Sow

The man-killing Crommyonian Sow ravaged the countryside around the Corinthian Isthmus. When Theseus was en route to Athens from Troizenos, he encountered the sow and it owner and killed them both. Pseudo-Apolldorus says both the owner and the sow were named Phaia and that the parents of the sow were thought by some to have been Echidna and Typhon, parents or Cerberus.Plutarch suggests that Phaia may have been a robber who was called a sow because of her manners.

Source: Theoi - Crommyonian Sow.