"He turned around, and there stood a marvellous horse, galloping on a large silver stone, broading a whispy green mane. It glared at Alex with fierce white eyes, staring into his soul, and it smiled a selection of sour, rotten teeth."
A Kelpie is a green horse that resides in water. They are often found in muddy lakes, oceans and rivers, some even living in garden ponds. Kelpies are renown for their extraction of children, and their gnarling, rotten teeth.