rycanada said:So the humanoid races that were made by the aboleths - I guess they weren't humans, elves, and dwarves, right? Don't both yuan-ti (in some form) and dragons predate humans in the core mythology?
According to the Forgotten Realms stuff, the amphibians were created by an amphibian race called the Batrachi, and the snake and lizard races (not dragons) were created by a serpentine race called the Sarrukh.
I credit the amphibians, fish, and oozes as aboleth creations. Like this:

FC2 seems to imply that the ancestors of the baatezu - called "angels" there - fought the obyriths alongside the Wind Dukes in the Time Before Time, incidently. Dragon #341 mentions an angelic race called aphanacts who ruled Mechanus and sought to conquer other planes in the name of Law - that sounds a lot like the race Asmodeus led into battle against the primordial demons.
It's possible (at least some of) the Elder Evils revered by the aboleths are the same as the draedens mentioned briefly in the FC1. If that's the case, they predate the gods and many of the planes but don't predate the multiverse itself. The multiverse was originally a primal void, a place where nothing, not even chaos, existed, and this was disturbed by the creation of the worlds, the elements, and the alignments (in whichever order you prefer).
Tharizdun, I think, was originally either a being of that primal void or a reaction against the void's pollution by the stuff of creation. Either way, he has nothing to do with the later Law and Chaos war, which was a dispute between two different flavors of creation rather than the earlier dispute between creation and nothingness.