Here is a list of mythical creatures beginning with this letter and I am constantly gathering information from each continent and continually updating.
Avalerion (Medieval)
Alerion (sometimes known as Avalerion) is a term for a heraldic bird. Historically, it referred to the regular heraldic eagle. Later, heralds used the term alerion to refer to "baby eagles" or "eaglets". To differentiate them from mature eagles, alerions were shown as an eagle displayed inverted without a beak or claws (disarmed).
To differentiate it from a decapitate (headless) eagle, the alerion has a bulb-shaped head with an eye staring towards the dexter (left-hand side) of the field. This was later simplified in modern heraldry as an abstract winged oval.