It's all about gut feeling. Purchase items to earn mastery rewards. The event ends on 21st July at 11:59 PM PDT.
*Offer ends on 21st July at 11:59 PM PDT. Only Items selling in the Marketplace are eligible for this reward. However, Items selling for less than 5 RP, Treasure Chest Items and Skill Point Reallocation do not count towards the prize.