The player's goal is to meet the seven Card Leaders around File Island and take from them the "7s" cards, which are required to reach Infinity Mountain, where all the data of the Digital World is processed, as well as to find the one who stole the Bug Card and bring it to the mountain, in order to revert the damage it caused and to prevent it from causing any further damage
The wait is officially over, Trainers
Defiler of Vigor Theres a whole cycle of Defilers in the set, which allow you to pay Phyrexian mana for their color of mana for any spell, and thats pretty crazy
Its role is further expanded in Pokmon Crystal, where players learn more about its origins through the lore centered around the Burned Tower in Ecruteak City
You can't choose a card you discarded with the effect of this card
But it does provide a glimpse at the authors intent: the high-level concept of Illusionary Mask is in the card name