Alberich changes to a dragon and then a toad in Das Rheingold, Scene 3.
Fafner changes to a dragon after the end of Das Rheingold and appears thus in Siegfried Act II. (It is never made clear whether Fafner actually used the Tarnhelm to transform, or simply transformed as many giants and gods did in the myths. There is also no Tarnhelm present in the original Andvari myth from Reginsmál in the Poetic Edda from which Wagner drew inspiration for this scene.)
Finally, it allows one to travel long distances instantly, as Siegfried does in Götterdämmerung, Act II.[1]
The stage directions in Das Rheingold and Siegfried describe it as a golden chain-mail helmet which covers the wearer's face.
In politics
Nacht und Nebel ("Night and Fog") was a directive of Adolf Hitler on 7 December 1941 that was originally intended to remove all political activists and resistance "helpers"; "anyone endangering German security" throughout Nazi Germany's occupied territories. The name was a direct reference to a magic spell involving the "Tarnhelm" ("stealth helmet") from Wagner's Rheingold.
In popular culture
In The Lord of the Rings, Éowyn adopts the name "Dernhelm" when she masquerades as a man before slaying the Witch-King of Angmar; "Dernhelm" is the Old English equivalent of "Tarnhelm".[2]