In Eberron, there is a feat called "Adamantine Body." This feat gives Warforged an armor bonus of +8, damage reduction 2/adamantine, -5 to armor check skills, only allows +1 to dex bonus to AC, and an arcane spell failure chance of 35%.
What the heck is damage reduction 2/adamantine? This is so foreign to me, it's not funny. Unfortunately, the campaign setting book is doing nothing for me. Anyone care to assist?