According to the artist:
"The Nuckelavee is an Orkney fae with the combined body of half a human and a horse, fins or flippers for legs, and no skin. Therefore, all its muscles and veins are exposed. The horse part of the Nuckelavee typically only has one large eye, although sometimes the human part does, too.

The Nuckelavee remains invisible when underwater, but when it comes on land, it takes on this grotesque form and kills livestock, crops and your family with sickness, plagues, droughts and natural disasters.

So naturally, I had to be a horrible person and draw a My Little Pony version of it!

_{PESTILENCE IS MAGIC!}"

Personally, I really rather like this. I'd like to see more mythological creatures get the MLP:FiM treatment.