Thank you Bryan Gustafson for the song suggestion.
A force of demons led by a powerful if relatively unknown servitor of Mammon (and backed by Baal) is making a play to colonize and privatize the sun. They have already captured or otherwise contained Galgaliel and destabilized Gabriel’s tether.
Should the party do nothing at all, hell will succeed; temporarily blacking out the sun. Only regions that return to their old sun rites (and whose native gods have come to an arrangement with the sun’s occupiers) will have access to its light. Others will be forced to rely upon fossil fuels as their crops begin to wither and their food chains collapse.