The party comes across a magic amulet. This amulet will give each user two wishes, but the wishes almost seem to have a mind of their own.
Missions for any campaign in any city of any realm. As long as crime exists, you will be able to use this submission.
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.