Tarnhelm

The Tarnhelm is a magic helmet made by the dwarf Mime on the orders of his brother Alberich. Alberich turns invisible with it and torments his brother, who had hoped to use the tarnhelm to steal the ring from Alberich, but was unable to work out how to use it before it was taken. When the Gods Wotan and Loge ask Alberich to demonstrate his power he turns himself into a serpent. Loge asks if he can become small and Alberich becomes a toad, but in this form he is captured and loses his treasure to the Gods. The treasure is then used to pay the giants Fafner and Fasolt for building Valhalla.

It may be that Fafner used the Tarnhelm to turn into the dragon, in whose guise he appears later on. When Siegfried kills Fafner, a bird tells him to take the ring and tarnhelm, although he doesn't know its power until its explained to him by Hagen. After Siegfried is given a love potion and falls in love with Gutrune, he agrees to take Brunhilda for Gutrune's brother Gunther. He uses the tarnhelm to disguise himself as Gunther and abducts Brunhilda, taking the ring from her. He also uses it to teleport to the Gibichung hall, leaving Brunhilde with the real Gunther unawares. However, it is later revealed the helm didn't fully conceal Siegfried, resulting in Brunhilde realizing what has happened after she sees him wearing the ring.

The fate of the Tarnhelm is unclear, although in an earlier draft of the libretto it is laid with the dying Siegfried and undone by the flames of his funeral pyre.