An MR item and an armor item that can't be penetrated
not sure if that's balanced or not, but what if? I think it would be cool. make it moderately expensive, and all it gives is 80-100 armor or 50-60 MR and their unique passives are that they cannot be penetrated or reduced in any way. you cant stack the item and it has no other effects or stats. Let's just say they each cost 2800 gold.