Sorcery Gems:

Used to place the first two basic stats on items up to two. These gems add magic attributes of all types (relative to the item you use the gem on) to armors, weapons, rings, bands, earrings and necklaces. These gems will only add one stat and also have the power to remove stats. These gems will not break an item and are also used for Master Skill Books.

Common place to find them are from bosses such as Draksel, Flesh eating butterfly, Kent.