Ixion, a mad man accused of kin slaying, was invited to the table of the gods after his exile as a show of mercy.

he lusted after hera, zeus' wife, so to test his faith zeus disguised a cloud nymph to look like his hera.

Ixion laid with the nymph and impregnated her, who gave birth to the first of the centaur.

zeus punished ixion for his transgression, failing his test of faith.