The Aurora Borealis

The Aurora Borealis is a naturally occurring phenomena over the high artic & sub-artic regions. Regularly caused by streams of solar wind hitting the magnetosphere, it gives off a spectacular light show as waves of colour are visible, especially at night. Greens and blues are common with tinges of other colours are observed. Old Cro-Magnon paintings show this effect and its significance, going back 30,000 years.
Most of the northern peoples have a mix of stories concerning the Aurora Borealis, with common features of these beliefs ranging that it is the ancestors talking or showing their presence to the living. Others being the gods themselves, whether playing or at war against others. Some of the stories also involve that fire makes this up and is found around many cultures including the Norwegians, who encountered it. They refer to it as norðrljós, or the Northern Lights.
Some have took to incorporating them into their myths & legends telling their young that no matter what the elders, ancestors & gods will always watch them when the time is right. That by reading the colours, shapes, and brightness they can work out what the hereafter is trying to tell them, along with the use of certain plant materials. Another one is the fire legends concerning the Aurora, stating that it is the fire that burns the other side of the world, or that sits around the edges of it holding everything in.
A few supernatural creatures also are aware of it and use it to their advantage. Many Fey will use it for good or ill depending on the type or personality of the Fey in question. Some like it and see it as a chance to entertain mortals, as well as a gateway to the Material Plane to bring gifts & joy to the world. Others see it as a chance to work dark magics and draw innocent mortals through to the worlds of the Dark Fey.

"It's spectacular, and definitely the ancestors communicating to us. That's what my mentor believes. An Arch Fey may be harder to work out than most of their kind, but their sincerity on this is palatable. Certainly they are likely to know, they do state that they have a deep connection to Alfheim, and Yggdrasil, and that it is the Vanir & Asgard both warring & feasting with teach other as well. They do this to attract the ancestors so they may feast & look upon their descendants to tell them this is where we will go to. That everything will be fine as long as the Northern Lights  appear, they will be watching with the gods from the other worlds at the top of the Great World Tree."
Bjorn the Warlock, and associate of Grimmaz the Axeman.