A land being plunged into chaotic energies, wild superstition, massive prejudices and distrust. More of a campaign setting than anything else.
This is more of a concept applied to a particular setting than the setting itself, bear this in mind.
When you sleep, your soul briefly returns to the place where it was created/goes to when it dies, and seeks nourishment. Everybody's soul is created with a little link (or you could say a greater entity calls it back) to that place so that it can return easily, but upon death, the soul returns via that and annihilates the link as if returns.
Also, as an added thingy, you could say the entity supplying the link, or residue of the links themselves, (whichever) is the source of all arcane power.