This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Fire Bird (Many cultures worldwide)
The Firebird is described in one of the texts collected by Alexander Afanasyev as having "golden feathers, while its eyes were like unto oriental crystal". Other sources portray a large bird with majestic plumage that glows brightly emitting red, orange, and yellow light, like a bonfire that is just past the turbulent flame. The feathers do not cease glowing if removed, and one feather can light a large room if not concealed.
A typical role of the Firebird in fairy tales is as an object of a difficult quest. The quest is usually initiated by finding a lost tail feather, at which point the hero sets out to find and capture the live bird, sometimes of his own accord, but usually on the bidding of a father or king. The Firebird is a marvel, highly coveted, but the hero, initially charmed by the wonder of the feather, eventually blames it for his troubles.