An alternate version of the beginning of the quest is that Bellerophon encountered Proetus, who grew intensely jealous of him.
Lycia at the time was in the middle of a horrific plague and Iobates didn't want to strain the population with a war, which would surely result if he murdered Bellerophon.
The goddess Athena, realizing Bellerophon would surely die if he undertook this task alone, sent him aid in the form of the winged horse, Pegasus.
To obtain the services of the winged horse, Polyidus told Bellerophon to sleep in the temple of Athena.
Iobates was unable to believe that this valiant hero deserved death, and so he allowed Bellerophon to marry his daughter.