Without the heroic action of Medea, Jason never would have obtained the Golden Fleece, neither would he have escaped from Colchis with it. He never would have become a figure of renown.
Without Medea, Jason would be a failure.
The narrative concerning the Argonauts, and their quest demonstrates that Jason’s success is delivered to him by the constant intervention of women; by goddesses and those descended from the god’s.
From the beginning of the narrative to the end Jason is watched over and looked after by Hera, queen of the god.
Hera persuades Aphrodite to send Eros, to instill in Medea a love for Jason, so that she would use her powers to help him against her father Aeetes. This is an example of divine selection, and it is the first indication that Medea is a person of Heroic quality.
As a result of her being stricken by Love with a passion for Jason, Medea gives him a magical ointment, with that Jason agrees to marry her.
Jason is welcomed to the court of Aeetes. He and the Argonauts are received as guests, but there is no friendship. Aeetes knows that Jason is in Colchis to obtain the Golden Fleece, he also knows that Jason has the favor of Hera. He cannot simply kill or dismiss Jason.
Instead he presents Jason with a number of challenges, so impossible and dangerous that any normal person would be killed in the attempt, and Jason is a normal person. He is not a king, and he is not the offspring of the gods. His power simply lies in the fact that he is a leader of men, he is unique in this, among the Hellenic heroes of this age.
Medea applies the ointment she has promised him, ensuring that Jason is protected from the lightening and fire of the monstrous oxen that Jason is tasked with subduing, consequently he was able to yoke the beasts, and plow the fields he was tasked with plowing, by harnessing their strength.
Her part in their marriage contract is complete.
Without the anointing that Medea gave him, he would have been dead. This is evidence of her own personal power as a witch or sorceress.
The power of witch craft (a woman’s power), commonly viewed by Hellenistic cultures as something to be feared and shunned, serves here as the salvation of one of its greatest Hellenic heroes.
Jason receives credit for yoking the oxen, and plowing the field, but the power that made it possible was Medea’s.