Medusa is a criminal-organization made up of urban-legend themed criminals. It was started by the Gorgon of the same name from Greek Myth.
Medusa is a global criminal cartel with a mystic nature, that has set up in Gotham City. It was created by the gorgon Medusa from Greek myth after she escaped from the Amazonian prison of Reform Island.
Medusa's intention behind the group was that she wanted to turn humans into monsters to join her army and make her Queen of Monsters. While doing this, she had her enforcers be themed after urban-legends.