How do mortals come up with this stuff? I'm going to go ahead and stop you there.
If you want to know what happened during the Age of Creation, you're not going to get anywhere by asking me. You'll have to pull a Tabris and go beyond just asking the oldest of the gods and outsiders and checking the Akashic record; you'll need to chase down the Eldest of the First World and Great Old Ones from beyond Creation and wake the hoariest of the long-lasting Wyrms and seek out the Titans where they've survived this long by hiding on the Chaotic planes. You'll need to bother the time dragons and irritate the irii, and perhaps, as Tabris did, even find it necessary to find a way of communicating with things each individually vaster than Pharasma and Yog-Sothoth combined, Things which view our world from angles orthogonal to the ultimate reality underneath reality.
And in the end, when you put your book together, you'll have a mess of contradictory stories, and you'll from this conclude that the past itself was contradictory, and the worst part is that you'll probably be right about it; Tabris wasn't censured nor The Book of the Damned censored for being wrong.
My own advice is not to bother.
Now, rules of thumb for working with magic...
Hm.