When you do have a read, it is devastating and when you know a format cold and are really on your game, the guessing can get scarily accurate
These cards are distinguishable from Beta cards in three significant ways: The border on the back of the cards is in gold instead of black
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Sources: TCG Player (Base Set Mewtwo, First Edition Rocket's Mewtwo, Mew & Mewtwo GX, Mewtwo ex, Mewtwo Gold Star, Rocket's Mewtwo ex, Shining Mewtwo, Mewtwo e-Card, Rocket's Mewtwo [Winner], Mewtwo [XY Evolutions Staff Prerelease]), PriceCharting (Base Set 1st Edition Shadowless Holo Mewtwo, Mewtwo Gold Star)
Red Blue Marco deck revolves around the Leaders effect, giving a Character -2,000 Power makes it easier for you to attack and KO