Perseus has been sent on a quest to get the gorgans head. Stheno and Euryale are immortal so the only one to kill was Medusa.
The story of Perseus is: A king in ancient Greece had a daughter, Diane, who was to have a son who killed him. He was afraid of death and locked Diane in a bronze tower to prevent her having a child Zeus, lord of the sky, came to Diane in the form of gold rain. Diane then had a child, Perseus. When the king found out he had a big cheast made and sent he the two out too sea. They ended up on the island Seriphos found by the fisherman Dictys. Perseus grew into a strong, handsome young man. King Polydectus wanted Diane as his queen - but Perseus wouldn't let that happen. The king held a banquet and made everyone bring a gift to him... but Perseus was poor and couldn't get a gift and made a foolish promise. To get the head of the gorgon.
Perseus didn't know where the gorgons were. Hermes and Athena come and gave him a sickel and a polished sheild and told him to the grey sisters and ask them how to find the nymphs who live at the back of the north wind. The nymphs gave him a bag to put Medusa's head in, a cap of darkness to make him invisable and wings of speed to got him out of there fast. He then headed to the lair. He quietly snuck in and saw many of Medusa's stone victims. In the corner of the room sleeping. He went to them and in one woosh Medusa's head was off of her body.A few seconds later her sister woke up and started chasing him but he snuck away with the cap. On the way home he saw a young girl chained to the rock screaming and the two watching crying. He flew down and asked what happened. They told him that they were the king and queen of the land and that was their daughter who had to be scarificed because the queen had boased that the girl on the rocks, Andromeada, was more beauiful than the ones of Poseidons court.
Perseus went down to the sea in time to see somethingracing through the sea. The sea monster had come. He drew out Medusa's head and showed the sea monster. The king and queen agreed that Perseus and Andromeada should marry. After the wedding they continued on their journey. Some time later they arived back on Seriphos and found out that Dictys had been imprisoned and Diane was the slave for Polydectes. Perseus marched into the throne room where there was a party going on and annouced "I have the head of Medusa," everyone started to laugh. "Show me then," Polydectes replied - drunk. Perseus took the head and everone looking at the eyes got turned into stone. Perseus went to his home island and wanted to test his strenght in the discus throw. He through the discus into the crowd and hit an old man in the head.
The old man turned out to be his grandfather. The prophecy came true. When Perseus and Andromeada died Zeus turned them into stars beside eachother so they could be together forever. Did you know that Perseus was the only hero to get a happy ending?