If you just want to stomp the game I think things are easiest with Squirtle and friends by far, since you can build it into a Rain Dance deck later and have something that's out of any of the CPU trainers' league, whereas Charizard and Venusaur aren't as competitively powerful(though Pokemon Center cheese with Venusaur is pretty entertaining...), but you can really get away with doing a decent version of whatever you feel like running so I'd just go with whatever you think sounds fun
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While you wont be able to play them in Historic, they will still be legal in Timeless
However, mana screw is significantly worse than mana flood, and I must ensure I hit my first handful of lands than worry about how I will fight mana flood
That said, because this Heralds Horn features an exclusive full-art Moogle artwork, it could be worth a premium once the Final Fantasy set ages
There's no chance your Tropical Island comes away unscathed when all you have protecting it is a single piece of cheap plastic you've been moving from deck to deck since Return to Ravnica