The each uisge is a Scottish Highland Water Horse.
Etymology
The Scottish Gaelic "each uisge" has endured several anglicizations, e.g. aughisky;
Family
It belongs to the same family of water horses as the Irish aughisky and the each uisce.
Powers
It is reputed to be the fiercest and most dangerous of the Water Horses, although the Cabyll-Ushtey runs close. Like the kelpie, it is a shapeshifter. It may appear as a gigantic bird or a handsome young man. The creature usually assumes human shape, attracts women, and can be recognized only by the water weeds in his hair.
Place
The water-horse inhabits salt water or large still bodies of inland water, and is thus distinguished from the kelpie inhabiting running water. Like its cousin, the [uisce], the each uisge is said to kill those who dare to ride it.
Story
Cautionary tales were once told how an each uisge once appeared as a pretty little pony to several little girls near Aberfeldy, Tayside (until 1974, Perthshire). As they mounted the pony, its back lengthened to accommodate them. Although the horse ran to and fro among the rocks, the children could not be unseated; next morning their livers floated to the top of a nearby lochan. A smith of the isle of Raasay vowed revenge when an each uisge devoured his beautiful daughter. Working with his son, he lured the each uisge with a roasted sheep and then held it tight in iron hooks until morning.