Medusa was once a beautiful woman who everyone admired. She was a priestess of the goddess Athena and always went to the temple to pray. One day when she was praying, Poseidon, the god of the oceans assaulted her.
Medusa thought that Athena would help her, but she was wrong. Athena couldn't punish Poseidon because he was a powerful god so she blamed Medusa for her assault and punished her instead. She caused her skin to wrinkle, gave her snakes for hair and a gaze that turned people into stone. She was then banished to an isolated island away from everyone.
On a Greek island, the evil King Polydectes ordered everyone to give him a gift. He knew that one young man, Perseus was poor and did not have one. It was part of a plan to get rid of Perseus so he could force his mother, Danae to marry him. Perseus promised him the head of Medusa as his gift. The gods helped Perseus - Athena gave him a shield and sword, Hades a helmet of invisibility and Hermes gave him winged sandals so he could travel long distances quickly.
Perseus first had to find out where Medusa lived. The only people who knew this were the Stygian nymphs, but Perseus didn't know where they lived. He visited the Graeae sisters who only had one eye that they shared between them. Perseus stole their eye as they were passing it around and only gave it back when they told him where the nymphs could be found. After visiting the nymphs to get the location of Medusa's island he flew there using Hermes sandals.
At Medusa's home, Perseus saw all the statues of the people she had frozen, however, Perseus was smart. He knew if he looked at Medusa directly he would also be turned into stone. So he walked backwards looking at the reflections in his shield. When he came across Medusa he closed his eyes, turned and chopped off her head with his sword. He put her head in a bag and flew home. As he flew, her blood dripped from the bag and turned into poisonous snakes.
When Perseus got back home he found his mother about to be married to Polydectes against her will. He called out to the King and took the head out of the bag. Polydectes looked at Medusa's head and was turned into stone. So Perseus saved his mother and became one of the best-known heroes of ancient Greece.