Of the principal sources that Wagner used in creating the "Ring" cycle, the Scandinavian Eddas – the Poetic Edda and the Prose Edda – provided most of the material for "Das Rheingold". These are poems and texts from 12th and 13th-century Iceland, which relate the doings of various Norse gods. Among these stories, a magic ring and a hoard of gold held by the dwarf Andvari (Wagner's Alberich) are stolen by the gods Odin (Wotan) and Loki (Loge) and used to redeem a debt to two brothers. One of these, Fafnir, kills his brother and turns himself into a dragon to guard the gold. The Eddas also introduce the gods Thor (Donner), Frey (Froh) and the goddesses Frigg (Fricka) and Freyja (Freia). The idea of Erda, the earth mother, may have been derived from the character Jord (meaning "Earth"), who appears in the Eddas as the mother of Thor.