Helmet of Invisibility

In classical mythology, the Cap of Invisibility (Ἄϊδος κυνέην (H)aidos 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.

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.

In classical mythology the helmet is regularly said to belong to the god of the underworld. Rabelais calls it the Helmet of Pluto, and Erasmus the Helmet of Orcus. The helmet becomes proverbial for those who conceal their true nature by a cunning device: "the helmet of Pluto, which maketh the politic man go invisible, is secrecy in the counsel, and celerity in the execution."

As the name implies, Hades owned the helmet. It was forged for him by Elder Cyclopses after he and his brothers Zeus and Poseidon freed them from Tartarus. He then used this helmet to great effect during the Titanomachy and was instrumental in routing the Titans.

Athena, the goddess of wisdom, battle, and handicrafts, wore the Cap of Invisibility in one instance during the Trojan War. She used it to become invisible to Ares when she aided Diomedes, his enemy. Her assistance even enabled Diomedes to injure the god of war with a spear.

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