The skill Robe Armor Mastery is a skill for blacksmiths and alchemists and unlocks with choosing these classes at level 20.
It increases the defense of robe armor items.
In-game description: Experience and training grant you bonus stats while wearing robe armor. Robe Armor means the Clarity Armor Set, Demon Armor Set or Divine Armor Set from Advanced Crafting.
In-game effect description: Advancing this skill increases bonus granted to stats.