A kelpie is a shape-shifting water spirit in Scottish folklore. It usually appears as a horse, but it can change itself into human form – a clue may be that the human has small pieces of water weed still in their hair. Sometimes the kelpie still has hooves instead of human feet.

The name comes from Gàidhlig cailpeach (pronounced approximately kal-uh-pyokh), which also means “calf” or “heifer.” There are very similar spirits in many other cultures. In German folklore, they are called necks or nixies. In Scandinavia, they are called bäckahäst. In Mayan and Aztec culture they were called wihwin. The Australian aborigines call them bunyip. The Welsh ceffyl dŵr and the Manx cabbyl-ushtey (both meaning “water horse”) are closely related.

With very few exceptions, kelpies are cruel and dangerous. They come out of the water, usually as a horse, to attract humans, who long to stroke them, or even to sit on their backs and ride them. But as soon as you touch a kelpie, your hand sticks fast to it, and it runs back into the water, taking you with it. Often the only sign that someone has been taken and eaten by a kelpie is a pile of human entrails left on the bank of the loch or river.

A legend first written down in the 19th century explains how the kelpies came into being. It is called in Gàidhlig Drochaid na Vougha, “Bridge of the Vougha” :

From the beginning of time, there was a band of tiny imps called the Mhougha (pronounced Voo-kha), whose home was the Firth of Dornoch. They lived close to the water, and their favourite food was fish and seafood of every kind. They had sharp little teeth and could crunch through mussel shells and crab claws with ease. They were so tiny that they crossed the water in cockle shells. For thousands upon thousands of years, they lived undisturbed in the wildest parts of Scotland, but mostly in and around the Firth of Dornoch, their ancestral home.

Then humans came, huge hairy beings that muddied the waters and stole all the fish. The humans were so clumsy and short-sighted, they often trampled the tiny homes of the Mhougha without even knowing they had done it. The Mhougha grew tired of running to escape the humans’ huge, hairy feet, and of seeing their homes destroyed.

So the King of the Mhougha went to speak with the chief of the humans. At first, the chief could not even see the king, because he was so tiny, and his voice was like the buzzing of a bee. But eventually the king managed to be heard, and explained why the Mhougha were so unhappy. The tribe considered what the king said, and explained that they had to bring their cattle to water, or they would die. Eventually, the king suggested a solution. The Mhougha were clever imps, and great builders. They would build a bridge that would allow the humans to cross from one side of the Firth to the other without trampling on the tiny Mhougha houses. The chief agreed.

The next morning, the tribe were astonished to see a bridge right across the firth, made entirely of sea-shells. It sparkled and gleamed in the sunshine, and was the most wonderful construction the humans had ever seen.

The chief was, of course, the first to cross the bridge. He mounted his splendid black horse and began riding across. But the horse was troubled. Like all horses, it was sensitive to spirits, and it could feel the spirits of the Mhougha all around. It began to prance and snort and whinny and neigh miserably. Eventually, the horse threw the chief over the wall of the bridge and into the water. Then the horse began pounding at the bridge with its hooves. Holes appeared. The sea-shell bridge could not withstand the constant leaping of the terrified horse and the constant pounding from its hooves. With a terrifying crash, the bridge collapsed and fell into the water, and the horse was drowned.

To this day, whenever one of the Mhougha comes out of the water and into the world of humans, it comes in the form of a great black horse, and it comes seeking revenge. If you ever see a beautiful black horse standing close to water, or with water dripping from its flanks, never touch it. Your hand will stick to it as if fastened by the strongest glue, and it will drag you into the water and eat you.