Rainbow lights

Finally, I have been waiting for a long time. I’ll be able to sleep for a couple of days now.

— Nessa inhabitant

This natural phenomenon happens above the only settlement, Nessa, on the once luscious planet of Areu. There is no rhyme or reason to when it happens and there are no scientific explanations for it either. The only constant with the phenomenon is that the Monsters don't attack for several weeks afterward. Some even say that the monsters disappear entirely as well. The earthquakes are supposedly a lot calmer. But there have not been any peer-reviewed studies done on that opinion.
Compared to other natural phenomena on this planet, the Rainbow lights happen relatively rarely. Once every other year or sometimes once a year. The longest time between times has been 3 years and 2 months.

It's beautiful isn't it? I'm happy that we happened to visit this week and not the next week as we had planned.

— A "tourist"

The lights are dancing across the sky in all the colors of the rainbow. People have tried to take photos or movies of the phenomenon, which has led a small group of scholars to believe that it is a collective hallucination. However, there are peer-reviewed studies that show that they happen. Or at least that the monsters stop coming while the lights are ongoing and even a couple of weeks after the event.
The lights usually start during early morning, and at first, they look like pillars of white light rising up from the ground. Then the sky looks like it's glittering for a couple of minutes before red lights starts dancing across the sky. The red light changes into orange and then into the other colors of a rainbow in the same sequence. The colors change quickly and most of the time it looks like it's a complete rainbow dancing across the sky. There will also be dots appearing that looks like stars, but these stars moves as well. The lights will then end with violet lights and then disappear...