In the campaign setting, it says that Aroden "disappeared". The Paizo staff have stated that, at least in their campaign, Aroden is really, really, dead. My thought was, since Aroden is basically the messiah, and has the power of prophecy, that he foresaw that if he continued to exist, it would start a chain of events that would destroy the world, possibly foreshadowed in the AP's, probably having to do with the horrors of the Dark Tapestry.
I believe that, in order for Aroden to save the world, he committed suicide, to avert the apocalypse and allow people to save the world. You know, proper Christ-figure self sacrifice.
So, in order for the apocalypse to restart, a group of evil (and good!) cultist set out to resurrect the living god in order to destroy the world like it was supposed to. The heroes (or villain) must race against time and just about everyone in the setting to stop the ritual from bringing the Savior/Destroyer back to life.
Does this sound like a good campaign idea?