The nuckelavee is the most malevolent of all water spirits, and is said to inhabit the wild coastlines of the remote Orkney Isles. Somewhat akin to the water-kelpie, the nuckelavee combines humanoid and equine elements. In appearance, it is often depicted as man's skinless torso rising from the back of a skinless horse - a truly terrifying marine visitation only enhanced by a single burning eye in the centre of the horse's head. In some ways, it is close in appearance to a centaur - albeit a thousand times more diabolical.
Its malevolence is said to be able to sicken crops and livestock, raise storms and bring droughts and disease when provoked - and provoking the nuckelavee is the very picture of ease. Burning seaweed - as the islanders often did in the 19th century - would cause it to rise from the depths and bring devastation onto the lands.
The nuckelavee is beyond the control of mortal man but can be evaded by crossing fresh water, through which it cannot pass.