Why did Perseus need Medusa's head?

Perseus was the son of the mortal Danaë and Zeus. When Perseus was a grown man, the king of Seriphos island(Perseus and Danaë were washed ashore and rescued by the king's brother, Dictys), Polydectes fell in love with his mother. read more

His mother, Danae, was being forced into marriage with King Polydectes of Seriphos who wanted access to the throne of Argos. read more

"I can bring you any present in the world, anything." he said. To get rid of him Polydectes told Perseus to bring back the head of the gorgon Medusa. While Perseus was away Polydectes set out to marry Danae. read more

So he sent Perseus on a quest to kill Medusa because he thought that she couldn’t be killed. He literally wanted Perseus dead just to have his mother to himself. Little did he know, Athena and Hermes aided Perseus on his quest to kill Medusa. He was offered many gifts and guidance in achieving the death of Medusa. read more