So, if you do Eberron, or a number of settings, a new set of core books might be required to cover the differences from the main 5e?No, you'd just need a "core supplement" of sorts to bridge the gap between core 3 and the setting; Xanathar's for a specific setting
— Mike Mearls (@mikemearls) July 11, 2017
So, if you do Eberron, a new set of core books might be required?
