This is a series of one-shot chapters that tell the stories of important events in griffon (and potentially world) history as pertains to the world built in Diplomacy for the Strong.
Chapter 1 - What is Griffonstone? How did a tiny decrepit village get the title of a Kingdom?
Chapter 2 - The Crystal Empire just accepts Cadance as their ruler? Why?
If you read these without the context of DftS, you do so with the understanding that this is expanded world-building and therefore innately head-canon territory. (Oh, and you won't really understand what's going on... so there's that too.)