2x EXP cards double the rate at which you earn experience (EXP) for defeating monsters or completing quests. So if you would normally earn 100 EXP from defeating a specific monster, you will earn 200 EXP when you have a 2x EXP card equipped. A 2x EXP card can be purchased in the "Character Modifications" → "EXP Coupons" category of the Cash Shop.
When purchasing a 2x EXP card, please first take note of the effect the drop card has, as well as the activation times for the card. The activation time and the duration of the cards will be placed on the description of the card itself. Please make sure to read these descriptions before purchasing a 2x EXP card.
There are special four hour and one day 2x EXP cards available for a one-time use. As soon as the card is purchased, the 2x effect will activate for the next four hours or one day, respectively.
IN ORDER TO SEE THE EFFECTS OF 2X EXP, THE CARD MUST BE PLACED IN YOUR CHARACTER'S ITEM INVENTORY. To transfer the item to your character, make sure to double-click on the 2x EXP card from the "Cash Inventory." The item will then be moved to the "Cash" tab of your item inventory. The 2x EXP effect will only be active on the character the card is equipped on.
The 2x EXP cards purchased from the Cash Shop will not stack with one another, meaning that if you buy two 2x EXP cards, you will not experience 4x EXP. However, the cards will stack with certain 2x EXP in-game events and with game functions that may also provide an increased EXP earn rate. Not all in-game EXP multiplier effects will stack, so please refer to the item description of the EXP effect before attempting to purchase a 2x EXP card.