I plan to "introduce" my players to an item down the road that is essentially a divining rod for portals scattered across the Realms. The item/artifact is alien in origin but they won't know much about it at first. It leads them to various portals but they don't know why. It will then be up to them to decide if they enter the portal and find out what's non the other side or not (some go to other planes, some don't). They'll also have to discover why the artifact is leading them to these portals and what will happen if they
don't enter the portals. Ooh, I'm nasty.