The Stars are Disappearing
This is a cause for concern. While there are other symptoms showing that the world is in danger, the missing stars are the most obvious.
Following an alignment of stars ten months ago, portals suddenly flared to life across this world which had been cut off from the planes for centuries. In some areas, organized baatezu armies poured into the world, taking people as slaves for the Blood War. In remote locations, however, infernal engines run as they have been since before memory, maintained by fiendish engineers.
Perhaps the world’s only hope may be curious planars who enter the world through the long-dormant portals.