Claws of the Dragon
“Ambient magic” is a general term for the level of magic in the world or, more accurately, the degree to which the physical world and Astral Space overlap.
This level changes in massive, poorly-understood cycles; the Scourge occurred at the zenith of this cycle, when the boundary between the planes became so insignificant, the Horrors were able to break through into the physical world to feed.
Theoretically, there would also be a counterpart to this high point, a nadir where there would functionally be no magic in the world.
After four hundred years of the Scourge, ambient magic levels dropped, but stopped before reaching what was thought to be, theoretically, at least, a safe state. This odd state has persisted for nearly a century and shows no sign of stopping. Some wonder if the cycle of magic has been halted. Some wonder if the Scourge has even ended at all…