This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Gytrash (Lincolnshire and Yorkshire)
The Gytrash, was a legendary shape-changer known in parts of the West Riding of Yorkshire. It was said to haunt lonely roads awaiting travelers. Appearing usually in the shape of animals (horses, mules, and dogs among others), the Gytrash haunt solitary ways and lead people astray, but they can also be benevolent, guiding lost travelers to the right road. They are usually feared.
The Gytrash is a shapechanging cousin of the Lincolnshire and Northamptonshire Shagfoal, of the Lancashire Skriker, of the Padfoot, also from the West Riding and of Barguest of much of the North Riding, Cumberland, Lincolnshire, County Durham and Northumberland. Gytrash are said to appear to wayward travelers.