...is what the "Dark One"'s goals are. It doesn't matter if it's Sauron/Morgoth, Shai'tan, Arawn, any of them. Yes, yes, they symbolize death. But when beings are personified and given kingdoms and agendas, those agendas start to sound silly. Okay, Morgoth, you conquered the world - what now? You can't really CREATE things. Doesn't existence become meaningless and boring?

Although the series was completely juvenile and stupid in a lot of ways, the second series of Dragonlance books showed this very well. Raistlin Majere managed to become a god, and the whole world was dead. How does one enjoy that, exactly? One doesn't.

Sanderson's Mistborn showed a good example of a "post-evil victory" world, but even then it turns out it wasn't really that.