What artifact makes its wearer invisible?

The story behind the answer

Helm of Darkness is correct because, in Greek myth, this is Hades’ magical cap that renders its wearer invisible—even to gods. Forged by the Cyclopes during the Titanomachy (alongside Zeus’s thunderbolt and Poseidon’s trident), it helped Hades move unseen. The helm also appears in heroic tales: Perseus borrows it to escape after beheading Medusa, and in the Iliad Athena uses it to act unnoticed in battle.

To remember: Hades = the dark Underworld, so his “Helm of Darkness” hides you in shadow. Think “Hades’ Helmet Hides.” The other choices sound plausible but aren’t authentic Greek artifacts, whereas the helm (also