According to mythology, it was made by the Cyclops. They had made a lightning bolt for Zeus, a trident for Poseidon, and the Helm of Darkness for Hades.[5]
The helm of darkness is also mentioned in Percy Jackson.
↑Ἄϊδος κυνέην (H)aidos kuneēn in Greek, meaning dog-skin of Hades
↑Michael W. Stewart (2006-08-15). "Helm of Hades (Cap of Hades)". Greek Mythology: From The Iliad To The Fall Of The Last Tyrant. Archived from the original on 2007-09-28. Retrieved 2007-05-05.