A man’s torso protrudes from a horse’s back resembling a male rider. The rider has no legs, but its arms can reach the ground from atop the horse’s body. In some versions the man’s head has that of a pig’s snout. The horse head has a solitary eye which burns like a red flame and a large mouth which emits a toxic vapor. Skinless, the Nuckelavee’s black blood courses through yellow veins. Its slick muscles are visible and the horse’s legs feed into fin-like limbs.
The Nuckelavee’s breath was said to wither crops and sicken livestock. Despite being a sea-dweller, the Nuckelavee was often attributed as the cause of droughts or illness. It was thought the smoke created from burning seaweed infuriated the Nuckelavee and encouraged its wrath. The Nuckelavee would seek revenge by killing livestock, causing water shortages or destroying crops.
Its only weakness was said to be fresh water. The Nuckelavee would not venture onto land during rain fall or cross fresh water streams. Those fleeing its presence would only have to cross a body of freshwater to escape its pursuit. During the summer months, the Nuckelavee is confined by the Mither o’ the sea – the only known spirit to contain it.