A Gaelic word meaning "water horse." The Ech-uisque was a goblin of Scottish Highland folklore, understood to be a favorite form assumed by the kelpie in order to lure souls to his master, the Devil. In the disguise of a fine steed, beautifully accoutered, the kelpie grazed innocently by the wayside. The weary traveler, passing by and believing this splendid animal to have strayed from his master, would be tempted to make use of him to help him on his way. The deceitful kelpie, remaining quiet as a lamb until the traveler was mounted, would then, with a fiendish yell of triumph, plunge headlong into an adjacent pool.
It was believed that the soul of the unfortunate man, who had no time to prepare for death, would thus be safely secured to the Evil One, while the kelpie received the body in payment for his trouble.