in #dnd 5e most devils have resistance to nonmagical
attacks that “aren’t silvered”
While demons don’t have silvered requirement?

Also, I noticed most demons have resistance to cold, fire, and lightening, while devils have resis. to cold & imm. to fire

I’m curious why

Part of it stems from legacy. The fire immunity thing on devils is because of the concept of "hellfire" and the medieval imagery of hell as a lake of fire, etc.

— Dan Dillon 👥 (@Dan_Dillon_1) March 4, 2020

The weapon material thing, in 3rd edition devils could be harmed my silvered weapons, while demons could be harmed by weapons made of cold iron. 5e didn't include cold iron as a special weapon material, though, so that wasn't carried forward.

— Dan Dillon 👥 (@Dan_Dillon_1) March 4, 2020

Thanks Dan! 😀
I’m glad I asked!Fey in prior editions also didn't like cold iron weapons.

You see a little of the concept expansion in that golems and a few other 5e constructs can be harmed by weapons made of adamantine.

But there were no rules for adamantine weapons until Xanathar's Guide to Everything.

— Dan Dillon 👥 (@Dan_Dillon_1) March 4, 2020