The youth Bellerophon admired the beauty of the winged horse, Pegasus, and hoped to capture it to make the horse his own. Seeking the help of the goddess Athena, he took the magic bridle which she gave him and set off to the Fountain of Pirene to lie in wait for Pegasus to come quench its thirst.

Bellerophon managed to leap atop the horse and got the bridle in its mouth, which instantly subdued the creature. The young man and Pegasus became close friends and flew through the skies together, coming to rest on Mt. Helicon, Pegasus' home.

Now King Iobates of Lycia was in search of a brave man to battle the dreaded Chimera, a fire-breathing creature with three heads; one of a lion, one of a serpent and the third of a goat. This creature had been laying waste to villages in Lycia, scorching them and killing their inhabitants. The King's son-in-law, Prietus recommended Bellerophon and Pegasus to fight the Chimera. The vase shows Bellerophon with a letter in his hand from Prietus, as Prietus waves farewell to him. Prietus' letter to Iobates not only recommended a hero, but also asked that Bellerophon be put to death, as Prietus was jealous of his wife's straying eyes. From this action, we get the modern expression of "Bellerophonic letters" which means any kind of communication that has content detrimental to the bearer.

Ancient Greeks believed strongly in the law of "filoxenia" or hospitality, which would definitely frown upon killing a visitor, so King Iobates rather just hoped that the Chimera would do in Bellerophon, thereby satisfying his son-in-law's demand. Instead, Bellerophon and Pegasus put up a terrific fight and killed the beast, returning to the palace as celebrated heroes. King Iobates, instead of killing him, gave Bellerophon the hand of his daughter and named him successor to the throne.

Bellerophon eventually met his downfall because of what the Greeks called "hubris". He began to think of himself as equal to the gods, and once when he approached Mt. Olympus on Pegasus, Zeus saw him coming, was enraged at his hubris and struck him blind and lame. He was destined to wander aimlessly for the rest of his life. Pegasus went back to being the horse of the Muses.