Wikipedia
Aitvaras is a goblin in Lithuanian mythology. It is also known by other names, such as Kaukas, Pūkis, Damavykas, Sparyžius, Koklikas, Gausinėlis, Žaltvikšas, and Spirukas. Aitvaras is identical to the Latvian Pūkis. An Aitvaras looks like a white or black rooster with a fiery tail ( meteorite). An Aitvaras may hatch from an egg of a 9- to 15-year-old rooster. If the Aitvaras dies, he becomes a spark.
In many cases, this Lithuanian creature is described as a bird and the appearance of a dragon outdoors. An Aitvaras will lodge itself in a house and will most often refuse to leave. It brings both good and bad luck to the inhabitants of the house. Aitvaras provide their adopted home with stolen gold and grain, often getting the household into trouble. According to many, an Aitvaras can be purchased from the devil - the price being that person's soul.