What bronze fire-breathing bulls did Jason have to yoke to obtain the Golden Fleece? They were the Khalkotauroi, the bronze bulls of Colchis.
The Khalkotauroi were two enormous bulls with bronze hooves and bronze mouths that breathed fire. King Aeetes set Jason the task of yoking them and using them to plough a field before Jason could claim the Golden Fleece.
According to the Argonautica, the god Hephaestus made the bulls and gave them to Aeetes. Jason survived their flames because Medea supplied him with a magical protective potion. After ploughing the field, he sowed it with dragon’s teeth, producing another deadly challenge: armed warriors who sprang from the ground.
The name comes from Greek words associated with bronze and bulls, and the creatures are also called the Colchis Bulls. They are not the Cretan Bull, which Heracles captured during his labours, nor the Calydonian or Erymanthian boars, which belong to separate heroic adventures.