[quote=@Dragoknighte]
Well, I have an idea that comes from a book series I read in middle school. There could be planes of existence layered on top of each other, like in photoshop. Layer one, that everyone can see is the material world. The more layers you can see, the more spirit activity becomes visible and the closer you get to the "true world." Spirits disguising themselves only masks them on certain layers. The better the disguise, the more layers they pass for human or whatever on. Gaining powers by selling your soul could automatically grant you access to being able to see the second layer, which would show which humans have their souls or not and allows them to see minor spirits and weak disguises. Or something of that nature.
[/quote]

Like a glamour?