Walking through the alleys of the docks district of town, you hear an old, mad beggar calling out for alms. He claims to be a god, cast out from heaven and stripped of his powers. The party passes, tossing a few coppers to him. In thanking them, the madman refers to incidents in their childhood or distant past which would have been all but impossible for him to know.
Real world scientists have accidentally opened a tear in the fabric of reality, transporting their laboratory into the game world. Unable to repair and/or refuel their equipment in this (to their minds) primitive world they are now trapped.