"Know, oh prince, that between the years when the oceans drank Atlantis and the gleaming cities, and the years of the rise of the Sons of Aryas, there was an Age undreamed of, when shining kingdoms lay spread across the world like blue mantles beneath the stars."
Dawnforge is a Primordial World setting by Greg Benage with help by Wil Upchurch and some others. Benage submitted this one to Wizards of the Coast in a competition for new and original settings. This one got knocked out in the semifinals but Fantasy Flight Games liked it and published it.
Plenty of settings - lookin' at you, Praemal - attempt Primordial. Dawnforge is the one that succeeded at getting across the atmosphere of a young and vital world.
Where the Hyborean Age (and Middle-Earth) purport to be records of the prehistory of this world Earth, Dawnforge suggests the prehistory of Generic Fantasy Setting Serial #QWER123. Quite often people complain that the backstory of - say - the Sea Of Dust in Greyhawk is more interesting than anything you're likely to do in there besides die of thirst and sunstroke. Who wouldn't want to check in on how the drow and the elves first fell out? Dawnforge lets you do that.
This is an age when human civilisation is young. The elves and the dwarves are still here. Elves struggle with drow, still just a sect; and dwarves fight, of course, giants.
Well phooey, we hear you say; what about dungeons, before there was anyone to build them. Here, Benage brought in serpentfolk. Yuan-ti in fact; we told you he was submitting this to WotC. The world's primordial for us apes - not for reptiles! Go right ahead and plop your yellowed copy of Tamoachan wherever you want. You can even call it Lubaatum if you want. Such ruins are best placed, where else, in the southern jungles of Zangala.
Another lot of baddies here are tieflings, whose Valhedar stands in for Howard's Acheron. In this world they're still active.