(Also, there's no "h" in Rovagug's name... nit picky, yeah, but if you're going to complain about a deity's name, it's good karma to spell the name right in your complaint.)
Especially Rovagug. After all, if you please him, he might let you live an extra couple of seconds.
Interestingly, Dragons Revisited notes that black dragons tend to avoid the Mushfens. (No, they don't care to talk about it.) But the River Kingdoms are supposed to have a few.
The Primer is also a good buy if you know zilch about Golarion and are wondering whether to invest only in the Pathfinder rules or in the setting as well. That probably doesn't apply to many here, of course, but that was why I picked it up.
Maybe Groetus is the laziest god in the multiverse, and all he's doing is casting himself as the PR face of the end times. You know--sit back with a frosty glass of lemonade and let Rovagug do all the heavy lifting.
Seems to me that the advantage of a long history is that it can never be overly detailed. Always plenty of room to slip in events important to your own game's backstory without rewriting the whole history in the process.