My last campaign was "stop the invasion". With the coming of 4e and the 3 tiers, I decided to go a bit larger in scope, and got the following.
Heroic: The players, who are refugees fleeing a dying world, set out to discover the new world. They unwillingly free an ancient evil (Aspect of Yeenoghu), letting it enter the mortal world where it can create havoc. During the course of the first tier, they learn a lot about the new world, including the fact that the gods that they worship (IE the PHB gods) are merely exarchs in this world, servants of ancient gods.
Paragon: Now big-time heroes, the players must untangle the mess they have created, stopping the horde of demons, undead and gnolls that Yeenoghu has unleashed on the world, only to discover how deep the rabbit holes goes.
Epic: Having defeated Yeenoghu and his posse, they find out that the whole thing is a plot by none other than Asmodeus. The twist is that the new gods (who are exarchs here) were originally the real gods in this world, but were sub-planted and killed by those who now claim they are the real gods. When they were killed, small parts of their divine essences hid in various mortals, who eventually became exarchs of the false gods. They have no memory of their former divinity, at least, most of them. Asmodeus does however, and he is setting the players up to ultimately topple the false gods and thus pave the way for the exarchs (IE the PHB gods) to assume their rightful place in the world.
So I guess it is kinda "the evil noble being in the scenes" campaign, just on a slightly larger scale.