Cap of Invisibility

"In classical mythology, the Cap of Invisibility is a helmet or cap that can turn the wearer invisible. It is also known as the Cap of Hades, Helm of Hades, or Helm of Darkness. Wearers of the cap in Greek myths include Athena, the goddess of wisdom, the messenger god Hermes, and the hero Perseus. The Cap of Invisibility enables the user to become invisible to other supernatural entities, functioning much like the cloud of mist that the gods surround themselves in to become undetectable." Source: Wikipedia