This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Brag (English)
A brag is a mischievous shapeshifting goblin in the folklore of Northumbria (Northumberland and Durham) and often takes the form of a horse or donkey. It is fond of letting unsuspecting humans ride on its back before bucking them off into a pond or bush and running away laughing.
One notable example is the Picktree Brag that was said to take other unusual forms such as a calf with a white handkerchief around its neck, a naked headless man, and even four men holding a white sheet. A brag at Humbleknowe was never seen but made hideous noises in the night.