Other iterations have the hydra grow when mana is spent or when it takes damage
The fact is, they can trade off with anything at any point in the game, and they pair extremely well with Rabid Bite variants
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Such is the case with Darkrai EX anyway, so consider switching one Nihilego for Giratina EX, giving rise to a new brand of the notorious DarkTina set (DragDarkTina, anyone?)
#4 Sol Ring Turn 1 Sol Ring is one of the best starts in oldschool (or any format where it is legal), and the advantage of four mana available turn two should be self evident
Common and uncommon cards Recent standard print cards Low demand rares These cards are usually sold in bulk lots