The Land of Argyle: The Argyle Lorebook (2007)

From the introduction:

In the beginning, there was Ko. Ko was everything, and everything was Ko. Where Ko gazed, Ko existed. This, of course, was a paradox: if Ko was everything, then Ko was also nothing. This was a cause of discomfort for Ko, and the entity sought to create structures outside of itself. Ko created the sun, the stars, the moon, and the land, which he called Heim. Now there was something other than itself for Ko to gaze upon. This too became wearisome after a time, and Ko sought to add to this creation. Creatures were placed upon the surface of Heim, a myriad of life of all sorts imaginable, and above all life Ko added Human, endowing the Human with strength, vigour, intelligence and determination. This occupied Ko for many eons, as Ko sought to perfect the creations.

User summary:

A developed campaign setting that includes minor variant rules (primarily regarding modifications to the standard races).