In Greek mythology, the Colchis Bulls were created by the god Hephaestus, and were given to King Aeetes as a gift. They are made from bronze, their horns are silver, and their eyes are rubies. When Jason came to Colchis in order to obtain the Golden Fleece, King Aeetes had him yoke the Colchis Bulls and use them to plough a field. The field was then to be sown with dragon's teeth. Jason managed to resist the burning flames of the Colchis Bulls due to a potion that was given to him by Medea.
Two Colchis Bulls attack Camp Half-Blood, being able to pass by the camp's borders because Thalia’s Tree was poisoned. After Annabeth gave Tyson permission to enter, he raced to Percy Jackson and smashed in the face of one of the bulls. The other is destroyed by the Camp's border patrol led by Clarisse. They are later used by the Hephaestus Cabin to make the tracks for the Chariot Races.
- They are made of bronze, which makes them hard to damage.
- They can breathe fire (the only defenses are Medea's Sunscreen, or being a creature immune to fire like Cyclopes or certain children of Hephaestus who have immunity against fire, like Leo).
- Their skin is burning hot.
- They can turn the top of their horns into spinning razor discs (film version only).
- Can spring forward a part of their back to stop people from climbing on top of them (film version only).
The Colchis Bull in the film seem to have the same role as the pair did in the book. The only noticeable difference being that it seem to destroy the magical borders of Camp Half-Blood, instead of just running through it. It manage to hit a few campers during its rampage until Percy destroys the bull by throwing Riptide into it, making it overheat, malfunction, and explode.