There are many individual components of a setting, but this tag is for the more meta of information.
There Are No Natural Halfbreeds
The Planar Council's Schools of Wizardry: Arcane Magic Colleges
The Divine Children: What is a God?
Introduction to Trigate, Part Ⅱ: Primordial Chaos and Teenage Dreams
Arcane Spellcasting: Choices to Be Made