Andvaranaut
Andvaranaut is the ring at the heart of the cursed gold of the dwarf Andvari, taken from him by Loki at the waterfall Gnitaheiðr after the god caught the dwarf in the shape of a pike. When Andvari was forced to give up his treasure hoard, he kept a single ring, and when Loki wrenched that away too, the dwarf laid a curse on the gold: it would destroy every possessor who came after him. The treasure passed to the chieftain Hreiðmarr as wergild for his murdered son Otr, then to the dragon Fáfnir, and finally to the hero Sigurðr, and ruin followed each owner. The story is told in the Völsunga sag