Champions of the Sun
Certain Charms and magical armor grant a trait called Hardness. Hardness offers protection from decisive attacks; it has no use against withering attacks. If a decisive attack’s damage dice pool is equal to or lower than the target’s Hardness, the decisive attack can’t inflict damage. A decisive attack that strikes but fails to penetrate the target’s Hardness is still considered a successful attack, and causes Initiative to reset to 3 as normal. Unlike soak, Hardness does not subtract from an attack’s damage.
Hardness doesn’t stacks unless it explicitly says so. If a character has Hardness from multiple sources, he simply uses the best Hardness value.