In Scandinavian folklore, a marmennill (also marmandill, marbendill, or margmelli) is a merman that often features in stories after having been accidentally caught at sea by fishermen.
[6] Stories about marmennill can be found in many modern Icelandic folklore collections, including in Jón Árnason's Íslenzkar þjóðsögur og æfintýri.
In exchange for his freedom, the creature reveals that he laughed at the farmer because his wife is unfaithful, his dog truly loves him, and the tuft of grass conceals a treasure.
[8] It has been noted that similar to the marmennill, some other beings in Scandinavian folklore could give indications on future events such as the sea monsters hafstramba and margýgr, which often are seen before storms and shipwrecks, and Óðinn, who in Böglunda sögur forbodes a large battle and death.
[9] Furthermore, in both Landnámabók and Hrafnkels saga Freysgoða there are account of a being appearing in the dream of a settler of Iceland, telling him to move to another part of the island.