This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Buggane (Manx)
In Manx folklore, a buggane (or boagane) was a huge ogre-like creature native to the Isle of Man. Some have considered them akin to the Scandinavian troll. A shapeshifter, the buggane is generally described as a malevolent being that can appear as a large black calf or human with ears or hooves of a horse. It was large enough to tear the roof off a church.
Its natural form is described as "covered with a mane of coarse, black hair; it had eyes like torches, and glittering sharp tusks". Another tale describes it as a huge man with bull's horns, glowing eyes and large teeth. As magical creatures, bugganes were unable to cross water or stand on hallowed ground.