In Greek mythology, Cycnus or Cygnus was a bloodthirsty and cruel man who dwelt either in Pagasae, Thessaly or by the river Echedorus in Macedonia.
Zeus parts Athena and Ares, while Kyknos flees in a chariot (right) as Heracles arrives (left), on an Attic black-figured volute-krater, c. 540–510 BCE signed by Nikosthenes (British Museum).
The Shield of Heracles is an archaic Greek epic poem that was attributed to Hesiod during antiquity. The subject of the poem is the expedition of Heracles and Iolaus against Cycnus, the son of Ares, who challenged Heracles to combat as Heracles was passing through Thessaly. It is generally dated from the end of the 7th to the middle of the 6th century BCE.
An early 5th-century BCE depiction of Heracles (left) fighting Cycnus (Attic black-figure amphora, found at Nola)