Stymphalids are similar in appearance and size to Cranes. They are man eating birds which their beaks and claws are made of brass, that can pierce armour. Their feathers are also made from brass which they can fire at men like arrows.
They are said to have come from the marshes in Arcadia. Hercules as one of his twelve labours was to rod the marshes of Stymphalids he did this by using brass rattles that scared the Stymphalids into the air where Hercules shot then down with arrows. Some of the Stymphalids escaped to the island of the war god Ares, where Jason and his crew encountered them on their way to collect the Golden Fleece. Jason's crew scared them off by banging their swords against their brass shields.