"Life Towers", jutting high into the atmosphere above even the mightiest of mountains, to where the air grew thin and unbreathable were erected worldwide to shed light and warmth on the world below once there was darkness. And so it came to pass that the sun finally went supernova...and the planet was sent careening off into space.
The Life Towers activated and preserved the planet. Project Perseverance went into stage two: plot out the planet's course through the universe and, if applicable, try to direct it so that it is captured by a young star in its prime and settled into the habitable zone. And so technology was eventually forgotten again...
The Life Towers are now collectively known as "Shadowbane". Shadowbane is beginning to fade. Shadowbane is beginning to whither. Cities and towns migrate away from the flickering, dieing Shadowbane and to the healthy, shining ones. But as Shadowbane continues to burn out, there is not enough room for everyone. Overcrowding forces masses of people to weaker Shadowbane. As these die, the teeming masses of Ahz'sun turn to war in order to claim healthy Shadowbane. Now, only three Major Shadowbane remain, underneath are the kingdoms of Aethanar, Sazine, and Greor. They are under siege from many of the countries existing underneath the Minor Shadowbane.
There's some of what was said. They shine light onto the world below them, in order to preserve the earth.