This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Gamayun (Russian)
Gamayun is a prophetic bird of Russian folklore. It is a symbol of wisdom and knowledge and lives on an island in the mythical east, close to paradise. She is said to spread divine messages and prophecies, as she knows everything of all creation, gods, heroes, and man.
Like the Sirin and the Alkonost, other creatures likewise deriving ultimately from the Greek myths and siren mythology, the Gamayun is normally depicted as a large bird with a woman's head. In the books of the 17th-19th centuries, Gamayun was described as a legless and wingless bird, ever-flying with the help of a tail, foreshadowing the death of statesmen by her fall.