Nuckelavee

Here is my version of the Nuckelavee (or Nuckalavee), a horrific and vicious type of water demon from Northern Scotland's folklore. It dwells in the sea, invisible, and seems to take a visible form only when it goes on land to torment humans or chase unlucky passers-by to drown them. Its breath is so foul that it wilts crops and sickens livestock, and the single eye of its horse head glows like a lighthouse. It is told that burning seaweed enrages the sea demon, which then causes epidemics and drought as a vengeance.
Luckily for the inhabitants of the Islands it haunts, the Nuckelavee doesn't tolerate fresh water, so crossing a river makes people able to escape it, and it doesn't go ashore when it's raining. Plus, during summer, it is confined to the sea by the Mither o' the Sea, a mightier marine spirit. This skinless monster is thought to be the result of a mix between the celtic Kelpie and another creature from Scandinavian folklore, imported to the Orkney Islands.