This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Hercinia (Medieval Bestiaries)
The hercinia was described in the 7th century, by Isidore of Seville stated, "Their feathers sparkle so much in the shade that, however dark the night is with thick shadows, these feathers, when placed on the ground, give off light that helps to mark the way, and the sign of the glittering feathers makes clear the direction of the path."
Hercinia are birds said to be from the Ercinian forest in Germany; where they are born, whose feathers so shine through the darkness; so that, although the night is dense, it is covered with darkness; to direct the journey to the garrison; let them shine brightly upon the earth, the course of which the road is open to the appearance of shining feathers.