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.
Just off the road a man lies dead, pierced through the heart from behind by an expertly thrown and ornate dagger which remains in the body. A long strip of cloth torn from the man's shirt has been tied around his neck; on the tag end an unknown hand has written a cryptic inscription: "For Djaygo."
When you get to the next town, everyone is talking about a mercenary woman found slain in exactly the same fashion in her room at the inn where she was staying.