Since you get to choose what card you discard, you can get rid of a GX or EX Pokemon in your hand, so there's no risk of it getting knocked out on the Bench, and Mewtwo and Mew-GX can take advantage of its attacks
As with other Secret Lair releases, the DnD drops do have a limited quantity, so if you are interested youll be probably want to snag them quickly before they sell out as the cards often spike significantly in value on the secondary market and on eBay
This new creature has the colors, name, types and power/toughness of the card you put on top of the pile, and the combined abilities of ALL creature cards in the pile including any other mutators you add to it later
and if you manage to get your hands on any of the expensive options on this list, someone will always be willing to take them off your hands
The beauty of the game is that it can be played together and thus has been translated on a global stage