Medusa with the Head of Perseus
Medusa is a Greek myth.  In the story, Perseus kills Medusa, not the other way around: Medusa is a monster with a face so terrible that anyone who sees her turns to stone.  Medusa lives on an island.  The hero Perseus comes to the island to kill Medusa.  He cuts off her head and puts it in a bag.  He later uses the head to turn his enemies to stone.  Perseus then gives Medusa's dead head to the gods.  Zeus puts Medusa's head on his shield so it will frighten his enemies.