Lith had seen plenty of powerful arrays surrounding lost cities and he knew that they couldn't emit such brilliance. The merfolk and Xoth had mentioned to the group the existence of a Forbidden Sun, but it would have been idiotic to waste its power to produce a light powerful enough to illuminate the seabed even from that distance.
A good mage would have focused its power so to guarantee the city protection and nurture the fields. Doing more would be pointless, wasting precious energy that could have been better employed to attack the barrier and further expand the city.
The source of light was Kolga itself. Tall buildings the size of a skyscraper had been erected right behind the barrier and from most of their glass windows came multi-colored lights that were spread and refracted by the array, producing the dazzling glow that Lith's group had seen from a distance.