A magus of the Light has discovered a ritual that can banish darkness from an area; as a firm believer in the dogma that darkness is where evil dwells, he feels it necessary to use this ritual to safeguard the town he is based in. While the Agents of Darkness that he so fears are nowhere near, the PCs are, and arrive not long after the ritual has taken place. Now, for roughly a league all around this town, darkness is no more; even in the depth of night, all is as bright as a summer’s midday, free from shadows.
Unfortunately, the world needs darkness, to have time to cool off and to let things of the day rest for a time. Now, the village is slowly growing warmer; the water of the nearby river is slowly dropping as it travels through the town, and the spike of hot air is disrupting the weather. Inhabitants are finding it difficult to sleep, tempers are fraying, and the crops are beginning to wilt.
Worse, the ritual had an unfortunate side effect, as it drew all the darkness into the mage who worked the ritual; now shadows clog his mind, and he is sliding into a paranoid state, convinced that the darkness beyond the edge of the light is waiting to devour him for his actions. Anyone seeking to restore the cycle of night and day will not only need to free the darkness from him, they’ll have to deal with a moderately powerful spellcaster who will see them as servants of the Darkness come to kill him.
1) Destroy the spell - The magic might be simple enough to remove, by a powerful enough caster, or it might require the party to learn the ritual from the mage and perform it in reverse. Or perhaps the party needs to find some equally strange ritual to bring the darkness back.
2) Showdown at High Noon - Perhaps the mage needs to be slain to release the shadows. Or perhaps he needs captured and the darkness drawn out magically; kill him, and his soul takes the darkness with it, condemning the area to eternal light.
3) Twins - The darkness within the mage may absorb some of his personality and awareness, such that when freed, instead of returning to the world as proper shadows and night, it becomes a Shadow-themed echo of the mage, complete with a ritual that can drain all the light from an area. Now the PCs need to deal with both mages in order to restore things.
4) Dupe - The ritual was actually a ploy by some evil agent hoping to corrupt and destroy the mage; the agent plans to reverse the ritual once the mage is irrevocably corrupted, and must be found and forced to work his ritual before the town is destroyed.
Beyond the moment
-Perhaps the PCs discover the town long after the mage has died and the inhabitants have all been forced to flee. What do they make of this strange, bright, hot place, a miniature desert in otherwise verdant lands?
-The forces of Darkness, it turns out, really do consider this an effront, and mount an assault on the settlement to find and destroy the source of this unnatural light. They may not be evil; nature spirits affronted by the disruption of normal cycles might be behind it, but that’s small comfort when an angry bear is breaking down doors at the command of a shadowy sprite.
-The effects of the heat bubble above the town begin to significantly alter the weather patterns of the entire region. The PCs might be dispatched to find out what is causing the trouble.