This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Boi-tata (Brazilian)
It is a myth from Brazil, Paraguay, Uruguay and Argentina, this creature is a huge fire serpent that appears and attacks against those who harm the forests and animals of the Amazon. He is the Brazilian equivalent of the will-o'-the-wisp. The name comes from the union of two Guaraní words mboi (snake) and tata (fire), the result being Mboi tata in the original language (Guarani) which means "Serpent of Fire".
It appears to be a green, orange, flame or black huge serpent with flames around his body, it's sometimes described by having two horns. A legend speaks of a mythical fire serpent who scares away loggers and that one day it discovered loggers cutting down the forest and burning trees. The serpent became so angry at the men for destroying the forest and polluting the air, that the light inside Boitata engulfed him and he became a fire serpent!