DISCLAIMER: Always keep empty space in your inventory at all times, especially when you're about to receive an item, and make sure that you are not overweight. The ExperienceRO team will not be held responsible for any items lost due to users' own actions. It is the players' responsibility to read the Rules and Regulations and the Warnings.
Mistress Card is an MvP card that is used to reduce 1 Gemstone from certain spells. Note that it only reduces one gemstone, so if you're using a skill like Abracadabra which requires 2 Gemstones, you will still need to provide one Gemstone.