What are the exactly the powers of Athena?
Athena is a real god in the series, Poseidon is her uncle.
However in Saint Seiya, she is actualy reborn as a mortal every 200 years or so. Her incarnation in the 20th century was taken from the Santuary by Kido Mitsumasa and adopted under the name Kido Saori. The other gods in Saint Seiya aren't reborn, they just posess mortals instead and can use their powers imediately. She is not initially aware of her identity/powers as Athena, but as the series goes on she shows all sorts of abilities, like telporting, healing, bestowing long life, sealing away other gods and fighting using her god cloth, staff and shield.