I'm with Chaos on this one; things like "ambient magic" are very un-Brandon. In his annotations on Elantris, he berates himself for having the source of the slime be something that couldn't be deduced from given information (even though it was just an ancillary touch of flavor). I can just imagine him cringing at phrases like "ambient magic." Let's not settle for that solution; it's a little too wave-of-the-wand.
By this you mean that Spren:[shard x]::Tears of Edgli:Endowment::Atium:Ruin::etc.? Now that might be something worth investigation
