<P> In classical mythology, the Cap of Invisibility (Ἅϊδος κυνέην (H) aïdos kuneēn in Greek, lit . dog - skin of Hades) 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 . </P> <P> One ancient source that attributes a special helmet to the ruler of the underworld is the Bibliotheca (2nd / 1st century BC), in which the Uranian Cyclops give Zeus the lightning bolt, Poseidon the trident, and a helmet (kyneê) to Hades in their war against the Titans . </P>

What was given to perseus to make him invisible