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Scalpers somehow managed to get their hands on hundreds of them before they had even made it into Happy Meal boxes, let alone the hands of the kids for which they were intended
To play the format you will need to construct a 100 card deck based around a commander - a legendary creature or planeswalker with the text at the bottom that says it can be played as your commander
The top cards are as follows: 228,000 Mega Charizard Y ex (Gold) ($1,436) 47,800 Pikachu ex (SIR) ($301) 39,800 Lillie's Clefairy ex (SIR) ($251) 17,800 Mega Feraligatr ex (SIR) ($112) 16,800 Mega Meganium ex (SIR) ($106) 16,800 Boss's Orders [Corbeau] (FA) ($106) 13,800 Mega Emboar ex (SIR) ($87) Pikachu ex and Lillie's Clefairy ex are more wanted than the Starter Mega Evolutions despite being 2x and 3.5x easier to pull, respectively
1xThe Ruinous Powers Commander Deck- Collector Edition