Shimmer-scale Dragons are a very beautiful breed with small—but highly reflective—scales that shimmer and shine as the dragon moves through water. They don’t have fins or webbed feet, but their long, eel-like bodies allow them to swim quite fast. They were once rumored to carry large pearls in their claws—causing many to seek them out in search of this fabulous treasure. In reality, the “pearl” is of greater value to the dragon, for the fabled treasure is actually an egg carried by a migrating female.
Moonlight Shadow loves to swim at night, by moonlight. He got a lot of romantic notions into his head from a book someone dropped (or threw) overboard. He can't read but there were many pictures of fairies dancing by moonlight and werewolves killing their one true love by accident and anguished lost souls and black roses and ravens and clocks striking midnight all day long.
After that kind of literature, it was no surprise that he fell for a Shadow Walker called 'Above The Winter Moonlight' who prefers to remain immaterial as much as possible.