This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Bolla (Albanian)
The bolla takes the form of demonic serpent possessing both cthonic and aquatic attributes. The bollar and errshaja are considered intermediate forms of this serpent as it goes through a series of metamorphoses. A reclusive, dragon-like creature cursed by St. George to remain blind and hidden away from society for much of the year.
This is likely the origin of the belief that for one day a year St. George's Day (April 23rd) the Bolla could open its eyes and roam freely, devouring anyone who falls within its sights. In time, the Bolla will evolve further. Its final form, known as the Kulshedra, is said to be even more fearsome, with 7-12 heads, red hair covering its body, pendulous breasts that drag along the ground, poisonous milk and urine, wings sprouting from its back, and the ability to spit fire.