Ghost Lion Crag i know there's greed and there's corruption

Arcturus let Wraen have free reign and before telling the third and the final story of the evening, she studied his face for a little while, searching for signs that would for impatience, barely contained tolerance or boredom. If there were any of those emotions within, the Moonspearan kept his expression stoic and did not let them betray him.

"It is about a vila and a prince. Vilas are mythical creatures - similar to fairies, nymphs, wood sprites. They are very, very beautiful and have a powerful magic. They can do good and give blessings to people they meet, but they can also become vengeful and cruel. And the story is about a vila, who fell in love. 

Once upon a time there lived a king and a queen and they had a son. When he was old enough, they held a big feast and performed the initation rituals into adulthood. And around midnight, when all the visitors had either returned home or gone to sleep, the prince went for a walk in the forest. And there in a meadow, among fragnant flowers and lights of fireflies he met a little vila.

She said: "I was too invited to your feast, but I did not have the courage to join the others, because I am so small. However, I am greeting you now in the moonlight." The prince was smitten with the little fairy-like creature and spent the night talking with her. By dawn he reached to embrace her and ask her to stay, but she ran away and disappeared, leaving only a tuft of soft and silky fur.

The following day the prince kept thinking about the vila and at midnight he found himself once again in the meadow, waiting for her to appear. It did not happen, until he touched the tuft of the fur and vila reappeared. This time she had grown up a bit. They spent this and the next nine nights meeting each other and talking, and by the tenth the prince had fallen so much in love with her that he asked her to stay.

Vila replied: "I will always come to you as long as the moon shines."
But the prince told her that he could no longer live without her and that he wished to make her the queen. The vila agreed saying: "My dearest prince, I will stay with you then, if you promise that you will always love me and me alone." The prince made that promise and the next day they were married.

Years passed and they lived as happily as it was possible, until one day the king died and many wolves from near and far came to pay the respects to him. Among them was a very beautiful princess, her coat shiny and black as coal, her eyes burning amber and trained on the prince from the very first moment. He was infatuated as well and his thoughts began to wander and muse. 

Vila saw this and the magic that had allowed her to remain in this world began to weaken. Over the next few days, as the prince paid less and less attention to her, she began to shrink, until one day she disappeared altogether. The prince did not mourn her and married the dark-furred beauty few days later. But he had not enjoyed his happiness for three days, when it turned out that the other girl was vicious, cruel and spiteful.

He exiled her and only then did he realize, what he had lost. He returned to the meadow, where he had first met vila for every night until the day he died, pleading her to return, but she never did," Wraen finished the story, stayed silent for a while, then got up and stretched. "That's enough for today, Arthur," she told him. "I have to head home, but I will probably see you around, won't I?" Wraen asked, ready to go, once the Moonspearan had said his farewells.

Bosnian folk-tale "Little Vila". By the way - Wikipedia says that J.K.Rowling's Veelas (Fleur Delacour) were inspired by these mythical beings of South-Slavic mythology.