My latest idea in my worldbuilding.
A group of powerful dragons used to have an empire. They created dragonborn to be soldiers, craftsmen, scholars, etc. They created kobolds to be menial servants. There was conflict between the dragons, leading to civil war. The surviving dragons fled to distant lairs. Dragonborn fled to villages on the edge of the empire.
Kobolds hid in the empire's tombs and monuments. They passed "the old ways" to later generations, but details got lost over time. Modern kobolds follow their teachings in a "cargo cult" fashion - eg, gathering shiny things to make a drag…