Goddess of the Earth. The Norns are her daughters. In Das Rheingold when the Chief God Wotan refuses to give the ring to the Giants she convinces him to, saying the end of the Gods is coming and the ring will cause this. He later seduces her and she bears him Brünnhilde.
She prophecys that when Alberich's son is born the end of the Gods is nigh. In the Opera Siegfried Wotan tells her he no longer fears the end and that her daughter Brunnhilde and Siegfried will be his heirs. At this point, Erda seems weakened "by the deeds of Men", and she sinks into eternal sleep, followed in Gotterdamerung by her daughters the Norns.