The Each Uisge (ach ushkeh) is a name for the Highland water horse, supposedly the most dangerous of the Scottish water dwelling fey creatures. The monster inhabited the sea, sea lochs and fresh water lochs.
The Each Uisge had the ability to shape shift, and could disguise itself as a fine horse or pony. To lure people into the water it would stand by the waters edge in one of these forms, and wait for somebody to approach. If a man mounted the horse, it would immediately set off into the deepest part of the loch, the rider being unable to free himself because he was stuck tight to the creature's skin. The unfortunate victim would then drown, and be devoured. Another disguise the Each Uisge could take was that of a handsome man, and because of the danger of these creatures, people were wary of lone animals and strangers standing by the waters edge,
Gethin touched the wild magic after Sholto and Meredith appeared in the Sluagh mound with a wounded Mistral in Swallowing Darkness and it becomes a Each Uisage.
It looked like a small back pony with big sharp teeth and flash of red in its eyes. Meredith made a common mistake and thought it a kelpie, a fey creature which is supposed to inhabit rivers and streams.