Long ago when the world was young there lived in the forest of Midgard a small fox named Rav who was as black as night. He was a sly little fox who liked to play jokes on the other animals of the forest. Needless to say, he didn't have many friends in the forest.
One day he was confronted by some rabbits that wanted to make fun of his abnormal black fur. He ran past them and swiped his tail over the grass in passing, lighting it into flames. The scared rabbits bound off in fear and hasted deep into the forest to escape the flames.
The land wright of the forest lake got upset with Rav and scolded the fox for causing such trouble. Rav tried to lie to the forest lake, telling her that he would not do such a thing again. But the forest lake knew better than to trust a fox and sent him from Midgard across Yggdrasil to Jotunheim, the land of giants and trolls.
Jotunheim is a cold, icy land, and there the fox found his lovely black coat had gone arctic white. Worse than that, now the little arctic fox was all alone and had to constantly flee from the giants and the trolls of the wild north. He did well at protecting only his own hide and the years passed before he knew it.
Then on a bitter cold day he spied a small fire where two travelers were eating. One had red hair and a beard and carried a mighty hammer. The other had black hair and seemed, to Rav, to be very cunning and fair. But as he was watching, the giants played a trick on the travelers by making the snow storm so hard the travelers could not find their way. Rav knew the lost travelers would come under attack by the giants soon.
It was then Rav felt regret for his own actions in the past and felt sympathy for the bold travelers. Running ahead, he swept his tail over the snow, sending up a whirl of fire into the sky making it like day. It was enough to startle the giants as he lit a path to the Bifrost bridge for the travelers.
At the top of the bridge one of the travelers companions could make out what was going on far below. He quickly alerted all in Asgard of the danger of the trouble making giants. So it was that in the end the travelers made it back to their land safely despite the snow storm.
Impressed with the little arctic fox they made Rav a small home at the base of the Bifrost bridge where it meets the frigid snow of the north. It would be the little arctic fox's duty to send up flames nightly so that anyone lost could see and find their way back home. He was so good at making his northern lights that they became known as the Foxfires or the Revontulet.