There speculation that the godkiller in the third campaign is there because Matt was privy to the new OGL under NDA and the main thing that ties the world he built to D&D is the pantheon. He makes his own monsters all the time, but he still has Vecna, the Raven Queen, the Wildmother, even though he gives them different names in some regions.

Sure would be a shame if something happened to that copyrighted material…

Cleverer still, in C2 and EXU he established that there is forbidden knowledge of ways that a mortal can become a god by replacing one. And when you kill a god, memory of your predecessor fades amongst mortals. Nobody human remembers the dead gods (I think it’s implied the other gods remember).

So if you can rewrite history such that only the gods remember the real story, but all of the gods are dead, you either have no pantheon or a new pantheon.