Shadow damage

Shadow damage is caused by a number of necromancer skills:
 * Dark Pact
 * Deathly Chill (if foe's Health is above 50%)
 * Spiteful Spirit (if hexed foe attacks or uses a skill)
 * Mark of Pain (if hexed foe takes physical damage)
 * Dark Aura (if enchanted ally sacrifices Health)
 * Desecrate Enchantments
 * Touch of Agony

Protection
Shadow damage ignores armor and there is no protection of any kind available specific to shadow damage.