According to the Prose Edda, he could change into an any form, and used to spend his days in the shape of an otter, greedily eating fish. Otr was slain accidentally by Loki. Hreidmar demanded a large weregild for Otr's death, namely to fill Otr's skin with yellow gold, and to then cover it entirely with red gold. When the skin was covered, one whisker was still protruding, forcing Loki to give up the ring Andvarinaut to hide it. The ring had been stolen from, and cursed by, the fish-dwarf Andvari. Greed for this cursed treasure ultimately caused the deaths of Hreidmar and his two surviving sons: Hreidmar was killed by Fafnir, who transformed into a dragon, and the other two were slain Sigurd's sword Gram.