Before any of his labors, Bellerophon needs Pegasus, the winged horse born from the blood of the slain Gorgon Medusa, and the seer Polyeidus tells him to sleep in Athena's temple, where the goddess appears in a dream and gives him a golden bridle. He wakes with the bridle in hand, finds Pegasus drinking at the spring of Pirene, and tames him with it on the spot.
Pegasus carries him through every labor Iobates sets, most famously the killing of the Chimaera, flying above the monster's reach to strike it down from the air. Success and royal favor, in the version of the story that ends least well for him, go to Bellerophon's head: he decides a hero who has killed the Chimaera and married a king's daughter deserves a place among the gods, and tries to fly Pegasus up to Olympus. Zeus, unwilling to let a mortal simply arrive uninvited among the immortals, sends a gadfly to sting Pegasus, who throws his rider back down to earth. Bellerophon survives the fall lamed and blinded, and spends the rest of his life wandering the Aleian plain alone, shunning the paths of other men, a fall from favor the ancient sources treat as the clearest lesson in Greek myth against a mortal overreaching toward the gods.