Mime

Mime is one of the Nibelung dwarves and brother to Alberich.

Das Rheingold
Alberich forces him to make the Tarnhelm when he enslaves the Nibelung. Mime planned to use it to steal the ring, but was unable to work out how to use it. Alberich realises Mime's plan. He uses the Tarnhelm to turn invisible and torments Mime. The Gods Wotan and Loge then find from Mime what Alberich has been doing. They are able to take the ring, tarnhelm and treasure from Alberich.

Siegfried
Before the opera Mime finds the dying Sieglinde in the Forest where the Giant Fafner guards the treasure in the form of a dragon, and is entrusted with the young Siegfried and the fragments of his father Siegmund's sword Nothung. Mime raises Siegfried, hoping to use him to slay Fafner and get the ring. However he is unable to reforge Nothung, and Siegfried breaks the swords he does forge. The God Wotan later wins Mime's head in a game of riddles and tells him the sword will be re-forged by one who knows no fear, he leaves Mime's head to this person. Siegfried soon after re-forges the sword, and Mime decides to kill him. Siegfried slays the Dragon, however when he tastes Fafner's blood he understands birds and is told Mime is planning to kill him, so kills the dwarf.