User blog comment:Hermione Chase/"The Blood of Olympus" Expectations/@comment-24030772-20131023134330/@comment-24082348-20131024042049

He fell off when Bellerophon was trying to fly to Mount Olympus, so Zeus sent a gadfly to sting Pegasus. Maybe Bellerophon will hold a grudge against the gods(like Heracles did) and try to make the quest harder for the 7.