Theyre strongly related to mana production and creature numbers, and very strong cards like Rofellos, Llanowar Emissary, Leovold, Emissary of Trest, and Priest of Titania, not to mention the support like Gaea's Cradle or Craterhoof Behemoth
Then spend 1 mana to turn Volrath into Grim Poppet, removing the -1/-1 counters from Volrath and putting them on other creatures, letting you machine-gun down opposing creatures while generating mana
I expect black aggro/recursive decks to adopt this guy, at least in Standard
After Giada, it's a real metagame strategy that competes with the best
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Snivy, Tepig, and Oshawott are also the only cards in this McDonalds set to feature artwork originally drawn by original Pokemon artist Ken Sugimori, who has been drawing for the franchise since its inception