There are two deities worshiped in Underlight, Shimmer (a moon god) and Shine (a sun god.) Relations between the worshipers of the two have been unsteady, and the past is riddled with wars.
Shimmer is the moon good. She promotes learning and knowledge. Priests of Shimmer primarily gain powers of insight, and very little with visible, physical consequences. Official and spiritual induction into the church requires one to give up one's greatest innocence (or ignorance; the idea behind it is choosing fact over speculation or fantasy, usually by learning a fact that dispels an illusion one has held all of one's life, but innocence is the official wording and of a great deal of significance to the quest.)
The followers of Shimmer are nocturnal, they prefer to remain active during the night and sleep (or at least remain behind tight shutters) during the day to avoid the sun's bright light.
One of the beliefs of the followers of Shimmer is that when an extremely faithful servant of Shimmer dies, their soul goes into the sky to become a star and spend eternity in the god's presence as a reward. Because of this, falling stars are believed to be either those who have fallen from Shimmer's good will, or messengers sent down by her to accomplish some task. Some versions of the story of Shining Son report that a falling star was seen on the night of his birth.
Shine is the sun god. He promotes hard work, especially working outdoors growing and cultivating under his watchful gaze. Priests of Shine gain powers of sustenance (including growing crops and such), energy, and healing (in roughly that order of power and availability.) Official induction into the church (and spiritually, into Shine's good light) requires one to give up their greatest luxury, lest it limit them and make them soft, and so that they may concentrate on their work.
The followers of Shine prefer to work in their god's light, so they are primarily active during the day.
One of the beliefs of the followers of Shine is that when an especially devout followers dies, their soul goes into the heavens and becomes one with Shine, augmenting his light and power. They believe this is one of the qualities that makes Shine superior, because he incorporates the souls into himself, gaining their strength and wisdom, instead of simply placing them in the sky as decorations.