I am both extremely excited and extremely frustrated by this...
...by which I mean, I've been planning to run this exact story for YEARS now, foreshadowing little bits of it across 3 separate full-length campaigns, and now I won't know whether or not to run my story or the much-easier, probably-just-as-good version written by Paizo (also +1 for the return of Crystal Frasier! I was super impressed with her work in War for the Crown!).
I've been introducing McGuffin Artifacts on the side, foreshadowed Nocticula as a future BBEG (even before I ran Wrath of the Righteous and REALLY turned it up to 11 with her there), and I've got a GooglyDoc full of notes connecting backstory bits of Tar-Baphon and Aroden. My plan was to have the heroes start as basically college students / apprentice Pathfinders and really build up a Harry Potter vibe in act 1, then turn it into a spooky Scooby-Doo story in act 2 by killing off the PCs mentor and having him entrust his conspiracy theory and all his collected notes to them and having the nonMythic PCs have to run away from Mythic Bad Guys. The conspiracy would have to do with Aroden's unique path to divinity, and why he was so much more powerful and special than the rest of the Ascended pantheon that followed him via the Starstone. Tar-Baphon enters the picture as both the object of Nocticula's interest (he knows more about Aroden than anyone else), and as a potential final-tier BBEG for the PCs to oppose.
My interpretation of established canon is that Aroden's death was a premeditated suicide to both subvert one of Pharasma's prophecies and to save Iomedae from her failure in the Starstone Trial... My extension of this canon is that it wasn't Aroden himself OR the consequences of the Trial which pulled the cosmically metaphorical trigger. While accomplishing his primary and secondary objectives, he knowingly or unknowingly stepped into a trap laid by Tar-Baphon by re-entering the material world, and now an unsealed Tar-Baphon (and Nocticula / the PCs) believes that his next resurrection will come with the full powers of divinity he stole from Aroden.
The endgame scene I desperately wanted to run was to have the PCs utterly unable to influence the final battle between Baphy and Nocticula, but to then present them with a final clue which leads them to a totally unexpected tilt that neither of the bad guys realize: Tar-Baphon's plan didn't work, and Aroden is still alive... as a level 3 Expert drained of all magic, mythic, and divine energy. He's an insane old fisherman in Absolam that the whole city considers to just be insane. He goes on about how he failed and the prophecy isn't subverted yet, and how an apocalypse is imminent that only he can prevent by reaching the Starstone again. The great big choice for the PCs would then be: Help Aroden by taking on the Trial of the Starstone and hauling him along to it, or kill him with their anti-Mythic McGuffin to instantly deny both Tar-Baphon and Nocticula the prize that they are currently destroying central Avistan over.
I'll be excited to see how many of Paizo's ideas overlapped with mine!