We have sent a special gift to every account! Only the character that gets the box is able to achieve the missions.
You can only get the gift in ONE character on your account. Once you get the box, right click on it and a new interface will open.
On the bottom side of the interface, there will be missions that needs to be achieved in order to open the box. Some boxes can be skipped if you have a Master Key. Once you open the box, you will receive some rewards through your special box (picture below) as so as the next mission box. New accounts will start with the gift binded to the account aswell. You can receive the gift on the special box, as showed on the picture below.
Master Key can be obtained in the cash shop. Have fun !