Vampires become more or less dangerous when the sun rises or sets. Werewolves appear when the moon is full.
Are there other fantasy creatures tied to different celestial bodies? Like Venus, the morning star, is a very visible feature in the sky that ordinary people would be aware of, and could make myths about.
@skyfaller You might enjoy "Venus Rising on Water" by Tanith Lee. (Sometimes the term "vampire" is stretched, canvas-like, to include it; but it's really a cosmic horror, second contact type story.)